I have a Hyper V cluster(2012) with a 2012 guest running 2012 acting as my file server.
My 2 hosts are connected to a gig switch stack which in turn is connected to my Dell MD3200i.
My file server has a "data" disk that is a VHD(fixed) on the iSCSI storage. As is it OS(dynamic)
I'm coping 200GB right now and only seeing data thoughtput of 8MB/sec.
When I check perfrmance on the file server the disk queue is huge. But when I check the queue for C: on the host, which is where the cluster storage appears to sit, its got a low if not no queue.
Also did a copy using the host and saw 58MB/sec so I'm happy the network should be able to pass the data.
Switch CPU is at 5%
Can anyone tell me what I'm doing wrong?
I am in the process of investigating some performance issues myself and I have noticed that VMs that have Fixed size VHDX files are experiencing a significant performance degradation. Using SQLIO as the test base, 64K random blocks are written at 40 - 60 MB/s for fixed disks but 400 - 600 MB/s for dynamic disks. I can also reproduce this on demand by converting and compressing the fixed disks. I am trying to find information on this and why we are experiencing this problem.
I would also add that this has been the same on an iSCSI CSV based cluster and SMB 3 share hosted VMs. Any information on this would be great. Thanks
ClusterSharedVolumes is a mount point, not the same volume as C:. So checking the queue depth for C: didn't tell you anything about your iSCSI device. You'll have to find the physical disk that corresponds to CSV, not to C: if you want this data.
I would suspect that your iSCSI disk isn't giving you the throughput you need.
I found that change my secondary hard drives on the VMs from IDE attached VHDs to SCSI attached VHDs made a big differnce
SCSI Fixed sized VHD 15-20MB/s
SCSI Dynamic VHD 60-70MB/s
I have only done this on a few machines so far, but its one for others to try.
Working on trying with more important servers next
Fixed VHD always performs better than Dynamic VHD in most scenarios by roughly 10% to 15% within the exception of 4K writes, where fixed VHD performs significantly better according to the Windows Server Performance Team Blog.
Hyper-V and VHD Performance - Dynamic vs. Fixed:
Witch doesn't match your tests, so I think you missed something in your configuration schema. Read the following guideline:
Performance Tuning Guidelines for previous versions of Windows Server:
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