SMB server on WIndows Server 2019 shows extremely slow read speed when the clients run Win10

Question

Hello,

I am currently suffering from extremely slow read speed from SMB sharing, the connection speed is less than 1Mbps for some NIC.
When the clients try to copy or read files from the SMB server, the connection speed would nearly immediately drop to ~1Mbps after a burst of normal connection speed. At the same time, the GUI shows no progress during the slow speed state. If I wait for several tens of seconds, the connection would suddenly show normal speed in a flash, with the GUI suddenly gain some progress, then drop back to ~1Mbps. If I wait for enough time, the transfer would still be finished. At the same time, locally accessing the same file from SMB server is nearly impossible while no issues for other files on the same drive. Besides, there is no issue for uploading file to the SMB server with speed~1000Mbps.
This problem seems to occur only if the SMB server runs Windows Server and the clients run Win10 (with latest update) and the SMB server is being accessed from some specific NIC.
Here are the cases I have tested:
NIC:
Hyper-V Virtual Ethernet Adapter no issue
ASIX AX88179 USB Gigabit Ethernet Adapter no issue
Intel I219-LM issue occur
Intel I210-T1 issue occur
Intel 82576 issue occur
Realtek USB GbE Family Controller issue occur

SMB Server (NIC: I219-LM):
Windows 10 1809 no issue
Windows Server 2019/2016 issue occur

SMB Client (NIC: I210-T1; SMB Server: Windows Server 2019)
Windows 10 2004/21H2 issue occur
MacOS 12.0.1 no issue
Note: I tried to boot Win10 2004 from that Mac device and the issue still occurs.

I checked this thread: https://social.msdn.microsoft.com/Forums/en-US/7bd0aa5b-eb95-40a8-a56d-c6013273665c/extremely-slow-smb-network-speed-server-2012-r2?forum=winserver8gen
The problem seems to be quite similar, but unfortunately its solution did not work in my case. I have tried disabling every offload function and RSS, and my NICs do not support DMA at all. I have checked my configuration that digitally encrypting and signing are not enabled. The issue still occurs.

I suppose it should be an OS-related problem. Any ideas about the possible reason?

The SMB server is running Windows Server 2019 17763.2510. All the drivers are up-to-date. The SMB Server configuration is as follows:
AnnounceComment :
AnnounceServer : False
AsynchronousCredits : 512
AuditSmb1Access : False
AutoDisconnectTimeout : 15
AutoShareServer : True
AutoShareWorkstation : True
CachedOpenLimit : 10
DurableHandleV2TimeoutInSeconds : 180
EnableAuthenticateUserSharing : False
EnableDownlevelTimewarp : False
EnableForcedLogoff : True
EnableLeasing : True
EnableMultiChannel : True
EnableOplocks : True
EnableSecuritySignature : False
EnableSMB1Protocol : False
EnableSMB2Protocol : True
EnableStrictNameChecking : True
EncryptData : False
IrpStackSize : 15
KeepAliveTime : 2
MaxChannelPerSession : 32
MaxMpxCount : 50
MaxSessionPerConnection : 16384
MaxThreadsPerQueue : 20
MaxWorkItems : 1
NullSessionPipes : HydraLsPipe,TermServLicensing
NullSessionShares :
OplockBreakWait : 35
PendingClientTimeoutInSeconds : 120
RejectUnencryptedAccess : True
RequireSecuritySignature : False
ServerHidden : True
Smb2CreditsMax : 8192
Smb2CreditsMin : 512
SmbServerNameHardeningLevel : 0
TreatHostAsStableStorage : False
ValidateAliasNotCircular : True
ValidateShareScope : True
ValidateShareScopeNotAliased : True
ValidateTargetName : True

Answer 1

confirmed the issue should be related to some kinds of virtual machine stuff.
bypass the vitrul route on xen hypersior is a workaround , i believe this should be a windows BUG.

same 2 VM. i add 2 network cards which connect the physical directlty to connect same hub on physical . the speed is very quick.

Answer 2

Hi there,

The condition which you described can be related to this. File copies sometimes start fast and then slow down. Follow these guidelines to verify this situation:

-This usually occurs when the initial copy is cached or buffered (either in memory or in the RAID controller's memory cache) and the cache runs out. This forces data to be written directly to the disk (write-through). This is a slower process.
-Use storage performance monitor counters to determine whether storage performance degrades over time.

If you observe slow transfers of files, consider the following steps:

-Try the file copy command for unbuffered IO (xcopy /J or robocopy /J).
-Test the storage speed. This is because file copy speeds are limited by storage speed.

Slow SMB files transfer speed
https://learn.microsoft.com/en-us/windows-server/storage/file-server/troubleshoot/slow-file-transfer

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Answer 3

I just fixed this issue. It is not related to the RSS or the offload, but some kinds of virtual machine stuff. The SMB server also hosts Hyper-V service with 1 VM connected to a Hyper-V switch in the internal network mode. When I deleted this Hyper-V switch, the issue was somehow gone. I suppose this is related to some virtualization stuff.
Then I tried to add another Hyper-V switch. As far as I see, just after I set up everything, when the VM was started and connected to the Hyper-V network, the issue came back again. So I suppose this is related to Windows itself.
To make VM connect to the internal network, I tried to set the Hyper-V switch to external network mode and combine it to the physical NIC (at which the issue occurred). Luckly it works for both VM and other physical devices. The issue is somehow fixed.

Answer 4

Set-NetAdapterAdvancedProperty -name "" -DisplayName "IPv4 Checksum Offload" -DisplayValue "Disabled" -NoRestart
Set-NetAdapterAdvancedProperty -name "" -DisplayName "Large Send Offload V2 (IPv4)" -DisplayValue "Disabled" -NoRestart
Set-NetAdapterAdvancedProperty -name "" -DisplayName "TCP Checksum Offload (IPv4)" -DisplayValue "Disabled" -NoRestart
Set-NetAdapterAdvancedProperty -name "" -DisplayName "Large Receive Offload (IPv4)" -DisplayValue "Disabled"

here is my solution for windows VM on xen Hypersior, actually the Set-NetAdapterAdvancedProperty -name "*" -DisplayName "Large Receive Offload (IPv4)" -DisplayValue "Disabled" is the really fix for this issue, only runing this also OK.
i noticed there is a ps comond for microsoft vswitch , you may double check this.