Troubleshoot Azure File Sync sync health and errors

Article
11/21/2022
38 minutes to read

This article is designed to help you troubleshoot and resolve common sync issues that you might encounter with your Azure File Sync deployment.

Sync health

If I created a file directly in my Azure file share over SMB or through the portal, how long does it take for the file to sync to servers in the sync group?

Changes made to the Azure file share by using the Azure portal or SMB are not immediately detected and replicated like changes to the server endpoint. Azure Files does not yet have change notifications or journaling, so there's no way to automatically initiate a sync session when files are changed. On Windows Server, Azure File Sync uses Windows USN journaling to automatically initiate a sync session when files change.

To detect changes to the Azure file share, Azure File Sync has a scheduled job called a change detection job. A change detection job enumerates every file in the file share, and then compares it to the sync version for that file. When the change detection job determines that files have changed, Azure File Sync initiates a sync session. The change detection job is initiated every 24 hours. Because the change detection job works by enumerating every file in the Azure file share, change detection takes longer in larger namespaces than in smaller namespaces. For large namespaces, it might take longer than once every 24 hours to determine which files have changed.

To immediately sync files that are changed in the Azure file share, the Invoke-AzStorageSyncChangeDetection PowerShell cmdlet can be used to manually initiate the detection of changes in the Azure file share. This cmdlet is intended for scenarios where some type of automated process is making changes in the Azure file share or the changes are done by an administrator (like moving files and directories into the share). For end user changes, the recommendation is to install the Azure File Sync agent in an IaaS VM and have end users access the file share through the IaaS VM. This way all changes will quickly sync to other agents without the need to use the Invoke-AzStorageSyncChangeDetection cmdlet. To learn more, see the Invoke-AzStorageSyncChangeDetection documentation.

We are exploring adding change detection for an Azure file share similar to USN for volumes on Windows Server. Help us prioritize this feature for future development by voting for it at Azure Community Feedback.

Server endpoint health is in a pending state for several hours
This issue is expected if you create a cloud endpoint and use an Azure file share that contains data. The change enumeration job that scans for changes in the Azure file share must complete before files can sync between the cloud and server endpoints. The time to complete the job is dependent on the size of the namespace in the Azure file share. The server endpoint health should update once the change enumeration job completes.

Within each sync group, you can drill down into its individual server endpoints to see the status of the last completed sync sessions. A green Health column and a Files Not Syncing value of 0 indicate that sync is working as expected. If not, see below for a list of common sync errors and how to handle files that are not syncing.

A screenshot of the Azure portal

Go to the server's telemetry logs, which can be found in the Event Viewer at Applications and Services Logs\Microsoft\FileSync\Agent\Telemetry. Event 9102 corresponds to a completed sync session; for the latest status of sync, look for the most recent event with ID 9102. SyncDirection tells you if this session was an upload or download. If the HResult is 0, then the sync session was successful. A non-zero HResult means that there was an error during sync; see below for a list of common errors. If the PerItemErrorCount is greater than 0, then some files or folders did not sync properly. It is possible to have an HResult of 0 but a PerItemErrorCount that is greater than 0.

Below is an example of a successful upload. For the sake of brevity, only some of the values contained in each 9102 event are listed below.

Replica Sync session completed.
SyncDirection: Upload,
HResult: 0, 
SyncFileCount: 2, SyncDirectoryCount: 0,
AppliedFileCount: 2, AppliedDirCount: 0, AppliedTombstoneCount 0, AppliedSizeBytes: 0.
PerItemErrorCount: 0,
TransferredFiles: 2, TransferredBytes: 0, FailedToTransferFiles: 0, FailedToTransferBytes: 0.

Conversely, an unsuccessful upload might look like this:

Replica Sync session completed.
SyncDirection: Upload,
HResult: -2134364065,
SyncFileCount: 0, SyncDirectoryCount: 0, 
AppliedFileCount: 0, AppliedDirCount: 0, AppliedTombstoneCount 0, AppliedSizeBytes: 0.
PerItemErrorCount: 0, 
TransferredFiles: 0, TransferredBytes: 0, FailedToTransferFiles: 0, FailedToTransferBytes: 0.

Sometimes sync sessions fail overall or have a non-zero PerItemErrorCount but still make forward progress, with some files syncing successfully. Progress can be determined by looking into the Applied fields (AppliedFileCount, AppliedDirCount, AppliedTombstoneCount, and AppliedSizeBytes). These fields describe how much of the session is succeeding. If you see multiple sync sessions in a row that are failing but have an increasing Applied count, then you should give sync time to try again before opening a support ticket.

How do I monitor the progress of a current sync session?

Portal
Server

Within your sync group, go to the server endpoint in question and look at the Sync Activity section to see the count of files uploaded or downloaded in the current sync session. Keep in mind that this status will be delayed by about 5 minutes, and if your sync session is small enough to be completed within this period, it may not be reported in the portal.

Look at the most recent 9302 event in the telemetry log on the server (in the Event Viewer, go to Applications and Services Logs\Microsoft\FileSync\Agent\Telemetry). This event indicates the state of the current sync session. TotalItemCount denotes how many files are to be synced, AppliedItemCount the number of files that have been synced so far, and PerItemErrorCount the number of files that are failing to sync (see below for how to deal with this).

Replica Sync Progress. 
ServerEndpointName: <CI>sename</CI>, SyncGroupName: <CI>sgname</CI>, ReplicaName: <CI>rname</CI>, 
SyncDirection: Upload, CorrelationId: {AB4BA07D-5B5C-461D-AAE6-4ED724762B65}. 
AppliedItemCount: 172473, TotalItemCount: 624196. AppliedBytes: 51473711577, 
TotalBytes: 293363829906. 
AreTotalCountsFinal: true. 
PerItemErrorCount: 1006.

How do I know if my servers are in sync with each other?

Portal
Server

For each server in a given sync group, make sure:

The timestamps for the Last Attempted Sync for both upload and download are recent.
The status is green for both upload and download.
The Sync Activity field shows very few or no files remaining to sync.
The Files Not Syncing field is 0 for both upload and download.

Look at the completed sync sessions, which are marked by 9102 events in the telemetry event log for each server (in the Event Viewer, go to Applications and Services Logs\Microsoft\FileSync\Agent\Telemetry).

On any given server, you want to make sure the latest upload and download sessions completed successfully. To do this, check that the HResult and PerItemErrorCount are 0 for both upload and download (the SyncDirection field indicates if a given session is an upload or download session). Note that if you do not see a recently completed sync session, it is likely a sync session is currently in progress, which is to be expected if you just added or modified a large amount of data.
When a server is fully up to date with the cloud and has no changes to sync in either direction, you will see empty sync sessions. These are indicated by upload and download events in which all the Sync* fields (SyncFileCount, SyncDirCount, SyncTombstoneCount, and SyncSizeBytes) are zero, meaning there was nothing to sync. Note that these empty sync sessions may not occur on high-churn servers as there is always something new to sync. If there is no sync activity, they should occur every 30 minutes.
If all servers are up to date with the cloud, meaning their recent upload and download sessions are empty sync sessions, you can say with reasonable certainty that the system as a whole is in sync.

If you made changes directly in your Azure file share, Azure File Sync will not detect these changes until change enumeration runs, which happens once every 24 hours. It is possible that a server will say it is up to date with the cloud when it is in fact missing recent changes made directly in the Azure file share.

How do I see if there are specific files or folders that are not syncing?

If your PerItemErrorCount on the server or Files Not Syncing count in the portal are greater than 0 for any given sync session, that means some items are failing to sync. Files and folders can have characteristics that prevent them from syncing. These characteristics can be persistent and require explicit action to resume sync, for example removing unsupported characters from the file or folder name. They can also be transient, meaning the file or folder will automatically resume sync; for example, files with open handles will automatically resume sync when the file is closed. When the Azure File Sync engine detects such a problem, an error log is produced that can be parsed to list the items currently not syncing properly.

To see these errors, run the FileSyncErrorsReport.ps1 PowerShell script (located in the agent installation directory of the Azure File Sync agent) to identify files that failed to sync because of open handles, unsupported characters, or other issues. The ItemPath field tells you the location of the file in relation to the root sync directory. See the list of common sync errors below for remediation steps.

Note

If the FileSyncErrorsReport.ps1 script returns "There were no file errors found" or does not list per-item errors for the sync group, the cause is either:

Cause 1: The last completed sync session did not have per-item errors. The portal should be updated soon to show 0 Files Not Syncing. By default, the FileSyncErrorsReport.ps1 script will only show per-item errors for the last completed sync session. To view per-item errors for all sync sessions, use the -ReportAllErrors parameter.
- Check the most recent Event ID 9102 in the Telemetry event log to confirm the PerItemErrorCount is 0.
Cause 2: The ItemResults event log on the server wrapped due to too many per-item errors and the event log no longer contains errors for this sync group.
- To prevent this issue, increase the ItemResults event log size. The ItemResults event log can be found under "Applications and Services Logs\Microsoft\FileSync\Agent" in Event Viewer.

Sync errors

Troubleshooting per file/directory sync errors

ItemResults log - per-item sync errors

HRESULT	HRESULT (decimal)	Error string	Issue	Remediation
0x80070043	-2147942467	ERROR_BAD_NET_NAME	The tiered file on the server is not accessible. This issue occurs if the tiered file was not recalled prior to deleting a server endpoint.	To resolve this issue, see Tiered files are not accessible on the server after deleting a server endpoint.
0x80c80207	-2134375929	ECS_E_SYNC_CONSTRAINT_CONFLICT	The file or directory change cannot be synced yet because a dependent folder is not yet synced. This item will sync after the dependent changes are synced.	No action required. If the error persists for several days, use the FileSyncErrorsReport.ps1 PowerShell script to determine why the dependent folder is not yet synced.
0x80C8028A	-2134375798	ECS_E_SYNC_CONSTRAINT_CONFLICT_ON_FAILED_DEPENDEE	The file or directory change cannot be synced yet because a dependent folder is not yet synced. This item will sync after the dependent changes are synced.	No action required. If the error persists for several days, use the FileSyncErrorsReport.ps1 PowerShell script to determine why the dependent folder is not yet synced.
0x80c80284	-2134375804	ECS_E_SYNC_CONSTRAINT_CONFLICT_SESSION_FAILED	The file or directory change cannot be synced yet because a dependent folder is not yet synced and the sync session failed. This item will sync after the dependent changes are synced.	No action required. If the error persists, investigate the sync session failure.
0x8007007b	-2147024773	ERROR_INVALID_NAME	The file or directory name is invalid.	Rename the file or directory in question. See Handling unsupported characters for more information.
0x80c80255	-2134375851	ECS_E_XSMB_REST_INCOMPATIBILITY	The file or directory name is invalid.	Rename the file or directory in question. See Handling unsupported characters for more information.
0x80c80018	-2134376424	ECS_E_SYNC_FILE_IN_USE	The file cannot be synced because it's in use. The file will be synced when it's no longer in use.	No action required. Azure File Sync creates a temporary VSS snapshot once a day on the server to sync files that have open handles.
0x80c8031d	-2134375651	ECS_E_CONCURRENCY_CHECK_FAILED	The file has changed, but the change has not yet been detected by sync. Sync will recover after this change is detected.	No action required.
0x80070002	-2147024894	ERROR_FILE_NOT_FOUND	The file was deleted and sync is not aware of the change.	No action required. Sync will stop logging this error once change detection detects the file was deleted.
0x80070003	-2147942403	ERROR_PATH_NOT_FOUND	Deletion of a file or directory cannot be synced because the item was already deleted in the destination and sync is not aware of the change.	No action required. Sync will stop logging this error once change detection runs on the destination and sync detects the item was deleted.
0x80c80205	-2134375931	ECS_E_SYNC_ITEM_SKIP	The file or directory was skipped but will be synced during the next sync session. If this error is reported when downloading the item, the file or directory name is more than likely invalid.	No action required if this error is reported when uploading the file. If the error is reported when downloading the file, rename the file or directory in question. See Handling unsupported characters for more information.
0x800700B7	-2147024713	ERROR_ALREADY_EXISTS	Creation of a file or directory cannot be synced because the item already exists in the destination and sync is not aware of the change.	No action required. Sync will stop logging this error once change detection runs on the destination and sync is aware of this new item.
0x80c8603e	-2134351810	ECS_E_AZURE_STORAGE_SHARE_SIZE_LIMIT_REACHED	The file cannot be synced because the Azure file share limit is reached.	To resolve this issue, see You reached the Azure file share storage limit section in the troubleshooting guide.
0x80c83008	-2134364152	ECS_E_CANNOT_CREATE_AZURE_STAGED_FILE	The file cannot be synced because the Azure file share limit is reached.	To resolve this issue, see You reached the Azure file share storage limit section in the troubleshooting guide.
0x80c8027C	-2134375812	ECS_E_ACCESS_DENIED_EFS	The file is encrypted by an unsupported solution (like NTFS EFS).	Decrypt the file and use a supported encryption solution. For a list of support solutions, see the Encryption section of the planning guide.
0x80c80283	-2160591491	ECS_E_ACCESS_DENIED_DFSRRO	The file is located on a DFS-R read-only replication folder.	File is located on a DFS-R read-only replication folder. Azure File Sync doesn't support server endpoints on DFS-R read-only replication folders. See planning guide for more information.
0x80070005	-2147024891	ERROR_ACCESS_DENIED	The file has a delete pending state.	No action required. File will be deleted once all open file handles are closed.
0x80c86044	-2134351804	ECS_E_AZURE_AUTHORIZATION_FAILED	The file cannot be synced because the firewall and virtual network settings on the storage account are enabled, and the server doesn't have access to the storage account.	Add the Server IP address or virtual network by following the steps documented in the Configure firewall and virtual network settings section in the deployment guide.
0x80c80243	-2134375869	ECS_E_SECURITY_DESCRIPTOR_SIZE_TOO_LARGE	The file cannot be synced because the security descriptor size exceeds the 64 KiB limit.	To resolve this issue, remove access control entries (ACE) on the file to reduce the security descriptor size.
0x8000ffff	-2147418113	E_UNEXPECTED	The file cannot be synced due to an unexpected error.	If the error persists for several days, please open a support case.
0x80070020	-2147024864	ERROR_SHARING_VIOLATION	The file cannot be synced because it's in use. The file will be synced when it's no longer in use.	No action required.
0x80c80017	-2134376425	ECS_E_SYNC_OPLOCK_BROKEN	The file was changed during sync, so it needs to be synced again.	No action required.
0x80070017	-2147024873	ERROR_CRC	The file cannot be synced due to CRC error. This error can occur if a tiered file was not recalled prior to deleting a server endpoint or if the file is corrupt.	To resolve this issue, see Tiered files are not accessible on the server after deleting a server endpoint to remove tiered files that are orphaned. If the error continues to occur after removing orphaned tiered files, run chkdsk on the volume.
0x80c80200	-2134375936	ECS_E_SYNC_CONFLICT_NAME_EXISTS	The file cannot be synced because the maximum number of conflict files has been reached. Azure File Sync supports 100 conflict files per file. To learn more about file conflicts, see Azure File Sync FAQ.	To resolve this issue, reduce the number of conflict files. The file will sync once the number of conflict files is less than 100.
0x80c8027d	-2134375811	ECS_E_DIRECTORY_RENAME_FAILED	Rename of a directory cannot be synced because files or folders within the directory have open handles.	No action required. The rename of the directory will be synced once all open file handles within the directory are closed.
0x800700de	-2147024674	ERROR_BAD_FILE_TYPE	The tiered file on the server is not accessible because it's referencing a version of the file which no longer exists in the Azure file share.	This issue can occur if the tiered file was restored from a backup of the Windows Server. To resolve this issue, restore the file from a snapshot in the Azure file share.

Handling unsupported characters

If the FileSyncErrorsReport.ps1 PowerShell script shows per-item sync errors due to unsupported characters (error code 0x8007007b or 0x80c80255), you should remove or rename the characters at fault from the respective file names. PowerShell will likely print these characters as question marks or empty rectangles since most of these characters have no standard visual encoding.

Note

The Evaluation Tool can be used to identify characters that are not supported. If your dataset has several files with invalid characters, use the ScanUnsupportedChars script to rename files which contain unsupported characters.

The table below contains all of the unicode characters Azure File Sync does not yet support.

Character set	Character count
0x00000000 - 0x0000001F (control characters)	32
0x0000FDD0 - 0x0000FDDD (arabic presentation forms-a)	14
0x00000022 (quotation mark) 0x0000002A (asterisk) 0x0000002F (forward slash) 0x0000003A (colon) 0x0000003C (less than) 0x0000003E (greater than) 0x0000003F (question mark) 0x0000005C (backslash) 0x0000007C (pipe or bar)	9
0x0004FFFE - 0x0004FFFF = 2 (noncharacter) 0x0008FFFE - 0x0008FFFF = 2 (noncharacter) 0x000CFFFE - 0x000CFFFF = 2 (noncharacter) 0x0010FFFE - 0x0010FFFF = 2 (noncharacter)	8
0x0000009D (`osc` operating system command) 0x00000090 (dcs device control string) 0x0000008F (ss3 single shift three) 0x00000081 (high octet preset) 0x0000007F (del delete) 0x0000008D (ri reverse line feed)	6
0x0000FFF0, 0x0000FFFD, 0x0000FFFE, 0x0000FFFF (specials)	4
Files or directories that end with a period	1

Common sync errors

The sync session was canceled.

Error	Code
HRESULT	0x800704c7
HRESULT (decimal)	-2147023673
Error string	ERROR_CANCELLED
Remediation required	No

Sync sessions may fail for various reasons including the server being restarted or updated, VSS snapshots, etc. Although this error looks like it requires follow-up, it is safe to ignore this error unless it persists over a period of several hours.

A connection with the service could not be established.

Error	Code
HRESULT	0x80072ee7
HRESULT (decimal)	-2147012889
Error string	WININET_E_NAME_NOT_RESOLVED
Remediation required	Yes

This error can occur whenever the Azure File Sync service is inaccessible from the server. You can troubleshoot this error by working through the following steps:

Verify the Windows service FileSyncSvc.exe is not blocked by your firewall.
Verify that port 443 is open to outgoing connections to the Azure File Sync service. You can do this with the Test-NetConnection cmdlet. The URL for the <azure-file-sync-endpoint> placeholder below can found in the Azure File Sync proxy and firewall settings document.
```
Test-NetConnection -ComputerName <azure-file-sync-endpoint> -Port 443
```
Ensure that the proxy configuration is set as anticipated. This can be done with the Get-StorageSyncProxyConfiguration cmdlet. More information on configuring the proxy configuration for Azure File Sync can be found in the Azure File Sync proxy and firewall settings.
```
$agentPath = "C:\Program Files\Azure\StorageSyncAgent"
Import-Module "$agentPath\StorageSync.Management.ServerCmdlets.dll"
Get-StorageSyncProxyConfiguration
```
Use the Test-StorageSyncNetworkConnectivity cmdlet to check network connectivity to the service endpoints. To learn more, see Test network connectivity to service endpoints.
Contact your network administrator for additional assistance troubleshooting network connectivity.

Note

Once network connectivity to the Azure File Sync service is restored, sync may not resume immediately. By default, Azure File Sync will initiate a sync session every 30 minutes if no changes are detected within the server endpoint location. To force a sync session, restart the Storage Sync Agent (FileSyncSvc) service or make a change to a file or directory within the server endpoint location.

The user request was throttled by the service.

Error	Code
HRESULT	0x80c8004c
HRESULT (decimal)	-2134376372
Error string	ECS_E_USER_REQUEST_THROTTLED
Remediation required	No

No action is required; the server will try again. If this error persists for several hours, create a support request.

Sync failed because the operation was aborted

Error	Code
HRESULT	0x80c83000
HRESULT (decimal)	-2134364160
Error string	ECS_E_OPERATION_ABORTED
Remediation required	No

No action is required. If this error persists for several hours, create a support request.

Sync is blocked until change detection completes post restore

Error	Code
HRESULT	0x80c83075
HRESULT (decimal)	-2134364043
Error string	ECS_E_SYNC_BLOCKED_ON_CHANGE_DETECTION_POST_RESTORE
Remediation required	No

No action is required. When a file or file share (cloud endpoint) is restored using Azure Backup, sync is blocked until change detection completes on the Azure file share. Change detection runs immediately once the restore is complete and the duration is based on the number of files in the file share.

Sync failed because the sync database was unloaded.

Error	Code
HRESULT	0x80041295
HRESULT (decimal)	-2147216747
Error string	SYNC_E_METADATA_INVALID_OPERATION
Remediation required	No

This error typically occurs when a backup application creates a VSS snapshot and the sync database is unloaded. If this error persists for several hours, create a support request.

Sync can't access the Azure file share specified in the cloud endpoint.

Error	Code
HRESULT	0x80c8305f
HRESULT (decimal)	-2134364065
Error string	ECS_E_EXTERNAL_STORAGE_ACCOUNT_AUTHORIZATION_FAILED
Remediation required	Yes

This error occurs because the Azure File Sync agent cannot access the Azure file share, which may be because the Azure file share or the storage account hosting it no longer exists. You can troubleshoot this error by working through the following steps:

Sync failed because the request is not authorized to perform this operation.

Error	Code
HRESULT	0x80c86044
HRESULT (decimal)	-2134351804
Error string	ECS_E_AZURE_AUTHORIZATION_FAILED
Remediation required	Yes

This error occurs because the Azure File Sync agent is not authorized to access the Azure file share. You can troubleshoot this error by working through the following steps:

The storage account name used could not be resolved.

Error	Code
HRESULT	0x80C83060
HRESULT (decimal)	-2134364064
Error string	ECS_E_STORAGE_ACCOUNT_NAME_UNRESOLVED
Remediation required	Yes

Check that you can resolve the storage DNS name from the server.

Test-NetConnection -ComputerName <storage-account-name>.file.core.windows.net -Port 443

Verify the storage account exists.
Verify the firewall and virtual network settings on the storage account are configured properly (if enabled)

Note

An unknown error occurred while accessing the storage account.

Error	Code
HRESULT	0x80c8308a
HRESULT (decimal)	-2134364022
Error string	ECS_E_STORAGE_ACCOUNT_UNKNOWN_ERROR
Remediation required	Yes

Sync failed due to storage account locked.

Error	Code
HRESULT	0x80c83092
HRESULT (decimal)	-2134364014
Error string	ECS_E_STORAGE_ACCOUNT_LOCKED
Remediation required	Yes

This error occurs because the storage account has a read-only resource lock. To resolve this issue, remove the read-only resource lock on the storage account.

Sync failed due to a problem with the sync database.

Error	Code
HRESULT	0x8e5e044e
HRESULT (decimal)	-1906441138
Error string	JET_errWriteConflict
Remediation required	Yes

This error occurs when there is a problem with the internal database used by Azure File Sync. When this issue occurs, create a support request and we will contact you to help you resolve this issue.

The Azure File Sync agent version installed on the server is not supported.

Error	Code
HRESULT	0x80C8306B
HRESULT (decimal)	-2134364053
Error string	ECS_E_AGENT_VERSION_BLOCKED
Remediation required	Yes

This error occurs if the Azure File Sync agent version installed on the server is not supported. To resolve this issue, upgrade to a supported agent version.

You reached the Azure file share storage limit.

Error	Code
HRESULT	0x80c8603e
HRESULT (decimal)	-2134351810
Error string	ECS_E_AZURE_STORAGE_SHARE_SIZE_LIMIT_REACHED
Remediation required	Yes

Error	Code
HRESULT	0x80c80249
HRESULT (decimal)	-2134375863
Error string	ECS_E_NOT_ENOUGH_REMOTE_STORAGE
Remediation required	Yes

Sync sessions fail with either of these errors when the Azure file share storage limit has been reached, which can happen if a quota is applied for an Azure file share or if the usage exceeds the limits for an Azure file share. For more information, see the current limits for an Azure file share.

Navigate to the sync group within the Storage Sync Service.
Select the cloud endpoint within the sync group.
Note the Azure file share name in the opened pane.
Select the linked storage account. If this link fails, the referenced storage account has been removed.
Select Files to view the list of file shares.
Click the three dots at the end of the row for the Azure file share referenced by the cloud endpoint.
Verify that the Usage is below the Quota. Note unless an alternate quota has been specified, the quota will match the maximum size of the Azure file share.

If the share is full and a quota is not set, one possible way of fixing this issue is to make each subfolder of the current server endpoint into its own server endpoint in their own separate sync groups. This way each subfolder will sync to individual Azure file shares.

The Azure file share cannot be found.

Error	Code
HRESULT	0x80c86030
HRESULT (decimal)	-2134351824
Error string	ECS_E_AZURE_FILE_SHARE_NOT_FOUND
Remediation required	Yes

This error occurs when the Azure file share is not accessible. To troubleshoot:

Verify the storage account exists.
Ensure the Azure file share exists.
Verify the SMB security settings on the storage account are allowing SMB 3.1.1 protocol version, NTLM v2 authentication and AES-128-GCM encryption. To check the SMB security settings on the storage account, see SMB security settings.

If the Azure file share was deleted, you need to create a new file share and then recreate the sync group.

Sync is paused while this Azure subscription is suspended.

Error	Code
HRESULT	0x80C83076
HRESULT (decimal)	-2134364042
Error string	ECS_E_SYNC_BLOCKED_ON_SUSPENDED_SUBSCRIPTION
Remediation required	Yes

This error occurs when the Azure subscription is suspended. Sync will be reenabled when the Azure subscription is restored. See Why is my Azure subscription disabled and how do I reactivate it? for more information.

The storage account has a firewall or virtual networks configured.

Error	Code
HRESULT	0x80c8033e
HRESULT (decimal)	-2134375618
Error string	ECS_E_SERVER_BLOCKED_BY_NETWORK_ACL
Remediation required	Yes

This error occurs when the Azure file share is inaccessible because of a storage account firewall or because the storage account belongs to a virtual network. Verify the firewall and virtual network settings on the storage account are configured properly. For more information, see Configure firewall and virtual network settings.

Sync failed due to a problem with the sync database.

Error	Code
HRESULT	0x80c80219
HRESULT (decimal)	-2134375911
Error string	ECS_E_SYNC_METADATA_WRITE_LOCK_TIMEOUT
Remediation required	No

Error	Code
HRESULT	0x80c83044
HRESULT (decimal)	-2134364092
Error string	ECS_E_SYNC_METADATA_WRITE_LOCK_TIMEOUT_SERVICEUNAVAILABLE
Remediation required	No

These errors usually resolve themselves and can occur if there are:

A high number of file changes across the servers in the sync group.
A large number of errors on individual files and directories.

If this error persists for longer than a few hours, create a support request and we will contact you to help you resolve this issue.

The server failed to establish a secure connection. The cloud service received an unexpected certificate.

Error	Code
HRESULT	0x800b0109
HRESULT (decimal)	-2146762487
Error string	CERT_E_UNTRUSTEDROOT
Remediation required	Yes

This error can happen if your organization is using a TLS terminating proxy or if a malicious entity is intercepting the traffic between your server and the Azure File Sync service. If you are certain that this is expected (because your organization is using a TLS terminating proxy), you skip certificate verification with a registry override.

Create the SkipVerifyingPinnedRootCertificate registry value.

New-ItemProperty -Path HKLM:\SOFTWARE\Microsoft\Azure\StorageSync -Name SkipVerifyingPinnedRootCertificate -PropertyType DWORD -Value 1

Restart the sync service on the registered server.
```
Restart-Service -Name FileSyncSvc -Force
```

By setting this registry value, the Azure File Sync agent will accept any locally trusted TLS/SSL certificate when transferring data between the server and the cloud service.

A connection with the service could not be established.

Error	Code
HRESULT	0x80072ee2
HRESULT (decimal)	-2147012894
Error string	WININET_E_TIMEOUT
Remediation required	Yes

This error can occur whenever the Azure File Sync service is inaccessible from the server. You can troubleshoot this error by working through the following steps:

Verify the Windows service FileSyncSvc.exe is not blocked by your firewall.
Verify that port 443 is open to outgoing connections to the Azure File Sync service. You can do this with the Test-NetConnection cmdlet. The URL for the <azure-file-sync-endpoint> placeholder below can found in the Azure File Sync proxy and firewall settings document.
```
Test-NetConnection -ComputerName <azure-file-sync-endpoint> -Port 443
```
Ensure that the proxy configuration is set as anticipated. This can be done with the Get-StorageSyncProxyConfiguration cmdlet. More information on configuring the proxy configuration for Azure File Sync can be found in the Azure File Sync proxy and firewall settings.
```
$agentPath = "C:\Program Files\Azure\StorageSyncAgent"
Import-Module "$agentPath\StorageSync.Management.ServerCmdlets.dll"
Get-StorageSyncProxyConfiguration
```
Use the Test-StorageSyncNetworkConnectivity cmdlet to check network connectivity to the service endpoints. To learn more, see Test network connectivity to service endpoints.
Contact your network administrator for additional assistance troubleshooting network connectivity.

Note

Sync failed because the server was unable to decode the response from the Azure File Sync service

Error	Code
HRESULT	0x80072f8f
HRESULT (decimal)	-2147012721
Error string	WININET_E_DECODING_FAILED
Remediation required	Yes

This error typically occurs if a network proxy is modifying the response from the Azure File Sync service. Please check your proxy configuration.

Sync failed due to a problem with authentication.

Error	Code
HRESULT	0x80c80300
HRESULT (decimal)	-2134375680
Error string	ECS_E_SERVER_CREDENTIAL_NEEDED
Remediation required	Yes

This error typically occurs because the server time is incorrect. If the server is running in a virtual machine, verify the time on the host is correct.

Sync failed due to certificate expiration.

Error	Code
HRESULT	0x80c83078
HRESULT (decimal)	-2134364040
Error string	ECS_E_AUTH_SRV_CERT_EXPIRED
Remediation required	Yes

This error occurs because the certificate used for authentication is expired.

To confirm the certificate is expired, perform the following steps:

Open the Certificates MMC snap-in, select Computer Account and navigate to Certificates (Local Computer)\Personal\Certificates.
Check if the client authentication certificate is expired.

If the client authentication certificate is expired, run the following PowerShell command on the server:

Reset-AzStorageSyncServerCertificate -ResourceGroupName <string> -StorageSyncServiceName <string>

Sync failed due to authentication certificate not found.

Error	Code
HRESULT	0x80c80228
HRESULT (decimal)	-2134375896
Error string	ECS_E_AUTH_SRV_CERT_NOT_FOUND
Remediation required	Yes

This error occurs because the certificate used for authentication is not found.

To resolve this issue, run the following PowerShell command on the server:

Reset-AzStorageSyncServerCertificate -ResourceGroupName <string> -StorageSyncServiceName <string>

Sync failed due to authentication identity not found.

Error	Code
HRESULT	0x80c83079
HRESULT (decimal)	-2134364039
Error string	ECS_E_AUTH_IDENTITY_NOT_FOUND
Remediation required	Yes

This error occurs because the server endpoint deletion failed and the endpoint is now in a partially deleted state. To resolve this issue, retry deleting the server endpoint.

The volume where the server endpoint is located is low on disk space.

Error	Code
HRESULT	0x8e5e0211
HRESULT (decimal)	-1906441711
Error string	JET_errLogDiskFull
Remediation required	Yes

Error	Code
HRESULT	0x80c8031a
HRESULT (decimal)	-2134375654
Error string	ECS_E_NOT_ENOUGH_LOCAL_STORAGE
Remediation required	Yes

Sync sessions fail with one of these errors because either the volume has insufficient disk space or disk quota limit is reached. This error commonly occurs because files outside the server endpoint are using up space on the volume. Free up space on the volume by adding additional server endpoints, moving files to a different volume, or increasing the size of the volume the server endpoint is on. If a disk quota is configured on the volume using File Server Resource Manager or NTFS quota, increase the quota limit.

The service is not yet ready to sync with this server endpoint.

Error	Code
HRESULT	0x80c8300f
HRESULT (decimal)	-2134364145
Error string	ECS_E_REPLICA_NOT_READY
Remediation required	No

This error occurs because the cloud endpoint was created with content already existing on the Azure file share. Azure File Sync must scan the Azure file share for all content before allowing the server endpoint to proceed with its initial synchronization.

Sync failed due to problems with many individual files.

Error	Code
HRESULT	0x80c8023b
HRESULT (decimal)	-2134375877
Error string	ECS_E_SYNC_METADATA_KNOWLEDGE_SOFT_LIMIT_REACHED
Remediation required	Yes

Error	Code
HRESULT	0x80c8021c
HRESULT (decimal)	-2134375908
Error string	ECS_E_SYNC_METADATA_KNOWLEDGE_LIMIT_REACHED
Remediation required	Yes

Error	Code
HRESULT	0x80c80253
HRESULT (decimal)	-2134375853
Error string	ECS_E_TOO_MANY_PER_ITEM_ERRORS
Remediation required	Yes

Sync sessions fail with one of these errors when there are many files that are failing to sync with per-item errors. Perform the steps documented in the How do I see if there are specific files or folders that are not syncing? section to resolve the per-item errors. For sync error ECS_E_SYNC_METADATA_KNOWLEDGE_LIMIT_REACHED, please open a support case.

Note

Azure File Sync creates a temporary VSS snapshot once a day on the server to sync files that have open handles.

Sync failed due to a problem with the server endpoint path.

Error	Code
HRESULT	0x80c80019
HRESULT (decimal)	-2134376423
Error string	ECS_E_SYNC_INVALID_PATH
Remediation required	Yes

Ensure the path exists, is on a local NTFS volume, and is not a reparse point or existing server endpoint.

Sync failed because the filter driver version is not compatible with the agent version

Error	Code
HRESULT	0x80C80277
HRESULT (decimal)	-2134375817
Error string	ECS_E_INCOMPATIBLE_FILTER_VERSION
Remediation required	Yes

This error occurs because the Cloud Tiering filter driver (StorageSync.sys) version loaded is not compatible with the Storage Sync Agent (FileSyncSvc) service. If the Azure File Sync agent was upgraded, restart the server to complete the installation. If the error continues to occur, uninstall the agent, restart the server and reinstall the Azure File Sync agent.

The service is currently unavailable.

Error	Code
HRESULT	0x80c8004b
HRESULT (decimal)	-2134376373
Error string	ECS_E_SERVICE_UNAVAILABLE
Remediation required	No

This error occurs because the Azure File Sync service is unavailable. This error will auto-resolve when the Azure File Sync service is available again.

Note

Sync failed due to an exception.

Error	Code
HRESULT	0x80131500
HRESULT (decimal)	-2146233088
Error string	COR_E_EXCEPTION
Remediation required	No

This error occurs because sync failed due to an exception. If the error persists for several hours, please create a support request.

Sync failed because the storage account has failed over to another region.

Error	Code
HRESULT	0x80c83073
HRESULT (decimal)	-2134364045
Error string	ECS_E_STORAGE_ACCOUNT_FAILED_OVER
Remediation required	Yes

This error occurs because the storage account has failed over to another region. Azure File Sync does not support the storage account failover feature. Storage accounts containing Azure file shares being used as cloud endpoints in Azure File Sync should not be failed over. Doing so will cause sync to stop working and may also cause unexpected data loss in the case of newly tiered files. To resolve this issue, move the storage account to the primary region.

Sync failed due to a transient problem with the sync database.

Error	Code
HRESULT	0x80c8020e
HRESULT (decimal)	-2134375922
Error string	ECS_E_SYNC_METADATA_WRITE_LEASE_LOST
Remediation required	No

This error occurs because of an internal problem with the sync database. This error will auto-resolve when sync retries. If this error continues for an extend period of time, create a support request and we will contact you to help you resolve this issue.

Sync failed due to change in Azure Active Directory tenant

Error	Code
HRESULT	0x80c83088
HRESULT (decimal)	-2134364024
Error string	ECS_E_INVALID_AAD_TENANT
Remediation required	Yes

Verify you have the latest Azure File Sync agent version installed and give the Microsoft.StorageSync application access to the storage account (see Ensure Azure File Sync has access to the storage account).

Sync failed due to firewall and virtual network exception not configured

Error	Code
HRESULT	0x80c83096
HRESULT (decimal)	-2134364010
Error string	ECS_E_MGMT_STORAGEACLSBYPASSNOTSET
Remediation required	Yes

This error occurs if the firewall and virtual network settings are enabled on the storage account and the "Allow trusted Microsoft services to access this storage account" exception is not checked. To resolve this issue, follow the steps documented in the Configure firewall and virtual network settings section in the deployment guide.

Sync failed with access denied due to security settings on the storage account or NTFS permissions on the server.

Error	Code
HRESULT	0x80070005
HRESULT (decimal)	-2147024891
Error string	ERROR_ACCESS_DENIED
Remediation required	Yes

This error can occur if Azure File Sync cannot access the storage account due to security settings or if the NT AUTHORITY\SYSTEM account does not have permissions to the System Volume Information folder on the volume where the server endpoint is located. Note, if individual files are failing to sync with ERROR_ACCESS_DENIED, perform the steps documented in the Troubleshooting per file/directory sync errors section.

Verify the SMB security settings on the storage account are allowing SMB 3.1.1 protocol version, NTLM v2 authentication and AES-128-GCM encryption. To check the SMB security settings on the storage account, see SMB security settings.
Verify the firewall and virtual network settings on the storage account are configured properly (if enabled)
Verify the NT AUTHORITY\SYSTEM account has permissions to the System Volume Information folder on the volume where the server endpoint is located by performing the following steps:

a. Download Psexec tool.
b. Run the following command from an elevated command prompt to launch a command prompt using the system account: PsExec.exe -i -s -d cmd
c. From the command prompt running under the system account, run the following command to confirm the NT AUTHORITY\SYSTEM account does not have access to the System Volume Information folder: cacls "drive letter:\system volume information" /T /C
d. If the NT AUTHORITY\SYSTEM account does not have access to the System Volume Information folder, run the following command: cacls "drive letter:\system volume information" /T /E /G "NT AUTHORITY\SYSTEM:F"
- If step #d fails with access denied, run the following command to take ownership of the System Volume Information folder and then repeat step #d: takeown /A /R /F "drive letter:\System Volume Information"

Sync failed because the Azure file share was deleted and recreated.

Error	Code
HRESULT	0x80c8027e
HRESULT (decimal)	-2134375810
Error string	ECS_E_SYNC_REPLICA_ROOT_CHANGED
Remediation required	Yes

This error occurs because Azure File Sync does not support deleting and recreating an Azure file share in the same sync group.

To resolve this issue, delete and recreate the sync group by performing the following steps:

Delete all server endpoints in the sync group.
Delete the cloud endpoint.
Delete the sync group.
If cloud tiering was enabled on a server endpoint, delete the orphaned tiered files on the server by performing the steps documented in the Tiered files are not accessible on the server after deleting a server endpoint section.
Recreate the sync group.

Sync detected the replica has been restored to an older state

Error	Code
HRESULT	0x80c80254
HRESULT (decimal)	-2134375852
Error string	ECS_E_SYNC_REPLICA_BACK_IN_TIME
Remediation required	No

No action is required. This error occurs because sync detected the replica has been restored to an older state. Sync will now enter a reconciliation mode, where it recreates the sync relationship by merging the contents of the Azure file share and the data on the server endpoint. When reconciliation mode is triggered, the process can be very time consuming depending upon the namespace size. Regular synchronization does not happen until the reconciliation finishes, and files that are different (last modified time or size) between the Azure file share and server endpoint will result in file conflicts.

Sync failed because the HTTP request was redirected

Error	Code
HRESULT	0x80190133
HRESULT (decimal)	-2145844941
Error string	HTTP_E_STATUS_REDIRECT_KEEP_VERB
Remediation required	Yes

This error occurs because Azure File Sync does not support HTTP redirection (3xx status code). To resolve this issue, disable HTTP redirect on your proxy server or network device.

A timeout occurred during offline data transfer, but it is still in progress.

Error	Code
HRESULT	0x80c83085
HRESULT (decimal)	-2134364027
Error string	ECS_E_DATA_INGESTION_WAIT_TIMEOUT
Remediation required	No

This error occurs when a data ingestion operation exceeds the timeout. This error can be ignored if sync is making progress (AppliedItemCount is greater than 0). See How do I monitor the progress of a current sync session?.

Sync failed because the server endpoint path cannot be found on the server.

Error	Code
HRESULT	0x80c8027a
HRESULT (decimal)	-2134375814
Error string	ECS_E_SYNC_ROOT_DIRECTORY_NOT_FOUND
Remediation required	Yes

This error occurs if the directory used as the server endpoint path was renamed or deleted. If the directory was renamed, rename the directory back to the original name and restart the Storage Sync Agent service (FileSyncSvc).

If the directory was deleted, perform the following steps to remove the existing server endpoint and create a new server endpoint using a new path:

Remove the server endpoint in the sync group by following the steps documented in Remove a server endpoint.
Create a new server endpoint in the sync group by following the steps documented in Add a server endpoint.

Server endpoint provisioning failed due to an empty server path.

Error	Code
HRESULT	0x80C80299
HRESULT (decimal)	-2134375783
Error string	ECS_E_SYNC_AUTHORITATIVE_UPLOAD_EMPTY_SET
Remediation required	Yes

Server endpoint provisioning fails with this error code if these conditions are met:

This server endpoint was provisioned with the initial sync mode: server authoritative
Local server path is empty or contains no items recognized as able to sync.

This provisioning error protects you from deleting all content that might be available in an Azure file share. Server authoritative upload is a special mode to catch up a cloud location that was already seeded, with the updates from the server location. Review this migration guide to understand the scenario for which this mode has been built for.

Remove the server endpoint in the sync group by following the steps documented in Remove a server endpoint.
Create a new server endpoint in the sync group by following the steps documented in Add a server endpoint.

Common troubleshooting steps

Verify the storage account exists.

Portal
PowerShell

Navigate to the sync group within the Storage Sync Service.
Select the cloud endpoint within the sync group.
Note the Azure file share name in the opened pane.
Select the linked storage account. If this link fails, the referenced storage account has been removed.

# Variables for you to populate based on your configuration
$region = "<Az_Region>"
$resourceGroup = "<RG_Name>"
$syncService = "<storage-sync-service>"
$syncGroup = "<sync-group>"

# Log into the Azure account
Connect-AzAccount

# Check to ensure Azure File Sync is available in the selected Azure
# region.
$regions = [System.String[]]@()
Get-AzLocation | ForEach-Object { 
    if ($_.Providers -contains "Microsoft.StorageSync") { 
        $regions += $_.Location 
    } 
}

if ($regions -notcontains $region) {
    throw [System.Exception]::new("Azure File Sync is either not available in the " + `
        " selected Azure Region or the region is mistyped.")
}

# Check to ensure resource group exists
$resourceGroups = [System.String[]]@()
Get-AzResourceGroup | ForEach-Object { 
    $resourceGroups += $_.ResourceGroupName 
}

if ($resourceGroups -notcontains $resourceGroup) {
    throw [System.Exception]::new("The provided resource group $resourceGroup does not exist.")
}

# Check to make sure the provided Storage Sync Service
# exists.
$syncServices = [System.String[]]@()

Get-AzStorageSyncService -ResourceGroupName $resourceGroup | ForEach-Object {
    $syncServices += $_.StorageSyncServiceName
}

if ($syncServices -notcontains $syncService) {
    throw [System.Exception]::new("The provided Storage Sync Service $syncService does not exist.")
}

# Check to make sure the provided Sync Group exists
$syncGroups = [System.String[]]@()

Get-AzStorageSyncGroup -ResourceGroupName $resourceGroup -StorageSyncServiceName $syncService | ForEach-Object {
    $syncGroups += $_.SyncGroupName
}

if ($syncGroups -notcontains $syncGroup) {
    throw [System.Exception]::new("The provided sync group $syncGroup does not exist.")
}

# Get reference to cloud endpoint
$cloudEndpoint = Get-AzStorageSyncCloudEndpoint `
    -ResourceGroupName $resourceGroup `
    -StorageSyncServiceName $syncService `
    -SyncGroupName $syncGroup

# Get reference to storage account
$storageAccount = Get-AzStorageAccount | Where-Object { 
    $_.Id -eq $cloudEndpoint.StorageAccountResourceId
}

if ($storageAccount -eq $null) {
    throw [System.Exception]::new("The storage account referenced in the cloud endpoint does not exist.")
}

Ensure the Azure file share exists.

Portal
PowerShell

Click Overview on the left-hand table of contents to return to the main storage account page.
Select Files to view the list of file shares.
Verify the file share referenced by the cloud endpoint appears in the list of file shares (you should have noted this in step 1 above).

$fileShare = Get-AzStorageShare -Context $storageAccount.Context | Where-Object {
    $_.Name -eq $cloudEndpoint.AzureFileShareName -and
    $_.IsSnapshot -eq $false
}

if ($fileShare -eq $null) {
    throw [System.Exception]::new("The Azure file share referenced by the cloud endpoint does not exist")
}

Ensure Azure File Sync has access to the storage account.

Portal
PowerShell

Click Access control (IAM) on the left-hand table of contents.
Click the Role assignments tab to the list the users and applications (service principals) that have access to your storage account.
Verify Microsoft.StorageSync or Hybrid File Sync Service (old application name) appears in the list with the Reader and Data Access role.

If Microsoft.StorageSync or Hybrid File Sync Service does not appear in the list, perform the following steps:
- Click Add.
- In the Role field, select Reader and Data Access.
- In the Select field, type Microsoft.StorageSync, select the role and click Save.

$role = Get-AzRoleAssignment -Scope $storageAccount.Id | Where-Object { $_.DisplayName -eq "Microsoft.StorageSync" }

if ($role -eq $null) {
    throw [System.Exception]::new("The storage account does not have the Azure File Sync " + `
                "service principal authorized to access the data within the " + ` 
                "referenced Azure file share.")
}

Troubleshoot Azure File Sync sync health and errors

Sync health

How do I monitor sync health?

How do I monitor the progress of a current sync session?

How do I know if my servers are in sync with each other?

How do I see if there are specific files or folders that are not syncing?

Sync errors

Troubleshooting per file/directory sync errors

Handling unsupported characters

Common sync errors

Common troubleshooting steps

See also

Feedback

Additional resources

Additional resources