"Backup failed because Azure Backup was unable to create a snapshot for the selected backup volume(s) due to insufficient space."

Question

"Backup failed because Azure Backup was unable to create a snapshot for the selected backup volume(s) due to insufficient space."

TH 101

Hi all,

Got a Windows 2012R2 Server (Physical machine) which has been happily backing up to a vault in Azure for a year or more. Back up is for the C: drive which is 500GB. Usually has around 50GB free space, yesterday the free space had dropped to 30GB and the backup job failed with:

"Backup failed because Azure Backup was unable to create a snapshot for the selected backup volume(s) due to insufficient space."

30GB seemed a pretty healthy amount of free space but thought this may have been the cause so I freed up another 60GB of space to take the total free space to 90GB. Yet it's still failing. The error is thus:

Severity
Critical

Alert
Backup failure

Backup item(s)
C:\ on MyServer.

Description
Backup failed because Azure Backup was unable to create a snapshot for the selected backup volume(s) due to insufficient space.

Recommended action(s)
Make sure that at least 1 GB of free space is available in each of the backed up volumes.

Time
November 11, 2021 9:22 UTC

Vault
MyVault

Given the volume in question (which i understand to be C:) has an awful lot more free space than 1GB, I'm at a bit of a loss to understand what the problem is here.

Can anyone suggest what i need to do to resolve this issue?

Thanks in advance

SadiqhAhmed-MSFT 25,381 Reputation points Microsoft Employee

2021-11-11T14:39:50.31+00:00

Hi@TH Welcome to Microsoft Q&A community forum!

As you can see on the following link, the cache folder volumes should have free space that equals at least 5-10% of the total size of backup data. https://learn.microsoft.com/en-us/azure/backup/backup-azure-file-folder-backup-faq#whats-the-minimum-size-requirement-for-the-cache-folder. Since there was a sudden drop in the free space to 50GB to 30GB that could be causing the backup job failure. For now, you can free up some space in C: drive or move the cache folder to a different drive. To further understand why there was drop in free space, we need to investigate the logs and that can be done through support request. Let us know if you need assistance reaching out to Azure technical support team.
TH 101 Reputation points

2021-11-11T17:00:06.883+00:00

Hi Sadiqh,

Thanks for the reply, that makes sense as to why it failed in the first place certainly. What I'm more confused about is why it still failed even after the free space was increased to 90GB. Should the backup not have started working once there was more space available?

Thanks
SadiqhAhmed-MSFT 25,381 Reputation points Microsoft Employee

2021-11-11T19:28:18.413+00:00

Have you followed these steps - https://learn.microsoft.com/en-us/azure/backup/backup-azure-file-folder-backup-faq#how-do-i-change-the-cache-location-for-the-mars-agent-

Reference: https://learn.microsoft.com/en-us/azure/backup/backup-azure-file-folder-backup-faq#manage-the-backup-cache-folder
TH 101 Reputation points

2021-11-15T11:20:32.6+00:00

Thanks for the suggestion but this server only has one drive so i can't move it to a different drive. Since the C: drive has 90GB of free space, i don't see why i should need to move this folder anyway. The C: drive is 500GB and there is 90GB of free space so surely this should be enough? The backups are still failing but i cannot understand why given how much free space there is. Am i missing something?

Thanks
SadiqhAhmed-MSFT 25,381 Reputation points Microsoft Employee

2021-11-16T05:48:50.513+00:00

This issue warrants a support investigation. Recommend you to raise a support ticket with Azure backup team for further investigation.

SadiqhAhmed-MSFT 25,381 Reputation points Microsoft Employee

2021-11-11T14:39:50.31+00:00

Hi@TH Welcome to Microsoft Q&A community forum!

As you can see on the following link, the cache folder volumes should have free space that equals at least 5-10% of the total size of backup data. https://learn.microsoft.com/en-us/azure/backup/backup-azure-file-folder-backup-faq#whats-the-minimum-size-requirement-for-the-cache-folder. Since there was a sudden drop in the free space to 50GB to 30GB that could be causing the backup job failure. For now, you can free up some space in C: drive or move the cache folder to a different drive. To further understand why there was drop in free space, we need to investigate the logs and that can be done through support request. Let us know if you need assistance reaching out to Azure technical support team.
TH 101 Reputation points

2021-11-11T17:00:06.883+00:00

Hi Sadiqh,

Thanks for the reply, that makes sense as to why it failed in the first place certainly. What I'm more confused about is why it still failed even after the free space was increased to 90GB. Should the backup not have started working once there was more space available?

Thanks
SadiqhAhmed-MSFT 25,381 Reputation points Microsoft Employee

2021-11-11T19:28:18.413+00:00

Have you followed these steps - https://learn.microsoft.com/en-us/azure/backup/backup-azure-file-folder-backup-faq#how-do-i-change-the-cache-location-for-the-mars-agent-

Reference: https://learn.microsoft.com/en-us/azure/backup/backup-azure-file-folder-backup-faq#manage-the-backup-cache-folder
TH 101 Reputation points

2021-11-15T11:20:32.6+00:00

Thanks for the suggestion but this server only has one drive so i can't move it to a different drive. Since the C: drive has 90GB of free space, i don't see why i should need to move this folder anyway. The C: drive is 500GB and there is 90GB of free space so surely this should be enough? The backups are still failing but i cannot understand why given how much free space there is. Am i missing something?

Thanks
SadiqhAhmed-MSFT 25,381 Reputation points Microsoft Employee

2021-11-16T05:48:50.513+00:00

This issue warrants a support investigation. Recommend you to raise a support ticket with Azure backup team for further investigation.

Answer 1

TH 101

After some back and forth with the Azure Microsoft tech support people, the solution which fixed the issue was as follows:

In Windows explorer, right click on the volume (in this case the C: drive), select “Configure Shadow Copies…”
Select the C:\ volume and click on settings and set to “No limit”.
Restart the Volume Shadow Copy service.

Then i left the auto backup job to run in MARS and it worked a-ok overnight.

Hope this is of some help to someone.

SadiqhAhmed-MSFT 25,381 Reputation points Microsoft Employee

2021-11-22T19:24:02.85+00:00

@TH Glad to know that support team provided solution to this issue.

Thanks once again for sharing the solution with Microsoft Q&A community. This would certainly be helpful to others who may hit this error.

"Backup failed because Azure Backup was unable to create a snapshot for the selected backup volume(s) due to insufficient space."

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