topic Poor I/O on VHD(x) with NetApp cDOT 8.3 and Hyper-v 2012 R2 in Microsoft Virtualization Discussions

Poor I/O on VHD(x) with NetApp cDOT 8.3 and Hyper-v 2012 R2

TARIQALIJAN — Thu, 05 Jun 2025 05:09:53 GMT

we have a strange issues where where with random IOPs the latency is 200ms and throughput is about 2MB where 100% read or Write is fine the latendy drops to 5-6 and the throughput goes above 200MB on VM running Hyper-v 2012 R2 over SMB 3 from cDOT 8.3. I have tested this with IOMeter.exe

I have tried with fixed VHDX, VHD, dynamic VHDX, VHD, SCSI and IDE all same reasult. attached is the IOMeter result.

VMs on SMB from Scale out File server works fine.

has anyone got any idea of what might be the cause and any suggestion.

Regards

Tariq

Re: Poor I/O on VHD(x) with NetApp cDOT 8.3 and Hyper-v 2012 R2

gman9 — Tue, 10 Mar 2015 00:08:53 GMT

@TARIQALIJAN wrote:
hi
we have a strange issues where where with random IOPs the latency is 200ms and throughput is about 2MB where 100% read or Write is fine the latendy drops to 5-6 and the throughput goes above 200MB on VM running Hyper-v 2012 R2 over SMB 3 from cDOT 8.3. I have tested this with IOMeter.exe

I have tried with fixed VHDX, VHD, dynamic VHDX, VHD, SCSI and IDE all same reasult. attached is the IOMeter result.

VMs on SMB from Scale out File server works fine.

has anyone got any idea of what might be the cause and any suggestion.

Regards
Tariq

The issue is because Netapp does not support the enhanced features of SMB 3 like SMB Direct, SMB Multichannel, etc. It only gives you ODX if you are going straight to the NetApp. A SOFS cluster gives you a lot of memory cache for your Hypervisors as well.

In my own opinion, no storage vendor is going to give you that full functionaility because it will lessen the likehood that you would consider a near future upgrade to the next storage platform.

Re: Poor I/O on VHD(x) with NetApp cDOT 8.3 and Hyper-v 2012 R2

TARIQALIJAN — Tue, 26 May 2015 21:11:15 GMT

old thread but just saw it and wanted to post how i got it resolved, the reason it was poor I/0 was that we had to specifically choose 4k block for testing in hyper-v although in VMWare it was jut fine.

also setting cifs shares symbolic link properities to null i.e. -symlinke "" helps in browsing the share.