Hyper-V and Server 2003 Disk Performance

[MrMike]

So, I converted my WHS to a Hyper-V virtual machine on 2008 R2 Enterprise.

Overall performance of my VMs is excellent, but I saw a serious decrease in disk performance. I'm using SCSI passthrough.

The first HDTune is the drive on the host, the second is the exact same drive on SCSI passthrough to the guest:

At first I was noticing my transfers over the network were noticeably slower and was about to fault the networking aspect of it. While it's possible there's an issue there as well, I can't be certain based on this.

Is 2003 disk performance in Hyper-V just bad, or is there something obvious I should be doing?

Specs
Athlon X2 5200+
ASUS M2N-LR
8GB DDR2 800
AOC-SAT2-MV8
2x WD360GD - RAID1 OS
1x WD1600YS
6x ST31500341AS

 

[VDiesel]

ICs installed in the VM?

 

[MrMike]

Yep. To specify further, the ST31500341AS drives in the VM are on a virtual SCSI controller which requires the ICs.

 

[VDiesel]

Yep. To specify further, the ST31500341AS drives in the VM are on a virtual SCSI controller which requires the ICs.

Strange. Performance should be very close to native speeds.

Couple of things I can think of to look at;
- be sure you have enough ram allocated to the VM otherwise page filing will slow everything down.

-if you're running other VMs that don't have IC tools installed, shut them down and test drive speed again.

-connect 1 of those drives to an ICH/MB port instead of the SM card, then pass it thru to the VM and compare if any differece. It could come down to an issue with the SM driver.

Good luck

 

[MrMike]

Thanks for the suggestions.

I had considered memory and already doubled what the VM had with no change. It has 1GB and there's only 390MB used. On the off chance it might be CPU, I gave it priority and gave it the other core as well.

The other VMs are two Server 2008 R2 and one Server 2008. I shut them all down and ran it again. There was a slight improvement, and it is repeatable. Unfortunately, it's still not native speeds.

By the way, the AOC is not in a regular PCI slot but a 133MHz 64-bit PCI-X slot which should be good for 1GB/s.

I had the 160GB and two of the 1.5TBs on the AOC, so I moved the 160GB and offlined the other 1.5TBs. No change. I moved one of the 1.5TBs used by the WHS VM to an onboard SATA port. No change.

I shut down all VMs but a 2008 R2 and added a 1.5TB to it's SCSI controller in passthrough. I got this:

I added 2 more 1.5TB drives to it out of curiosity. I booted the other 2008 R2 and 2008 VMs. Same result as above in both instances.

 

[nitrobass24]

I mean even with passthrough theres going to be some performance loss, as the guest OS has to make calls to the Host OS to make calls to the Hardware.

BTW those speeds are not bad.
They are not native....but nothing to worry about IMO.

 

[brandinb]

I think its possible your host is starved for memory.
You should leave atleast 2gb dedicated memory for the host operating system or some more.

I seem to remember that hd tune got higher scores then native hardware possibly because of a caching mechanism of the host operating system giving the small test pattern of hdtune a boost but it has been a while since i used that setup. I had the disk systems using the default ide emulation.

Can you try the ide mode and see the performance of the guest operating system?

 

[MrMike]

I mean even with passthrough theres going to be some performance loss, as the guest OS has to make calls to the Host OS to make calls to the Hardware.

BTW those speeds are not bad.
They are not native....but nothing to worry about IMO.

I agree that there should be a performance loss, but I think there is an issue with disk performance of a Server 2003 guest under Hyper-V as opposed to a 2008 guest.

I think its possible your host is starved for memory.
You should leave atleast 2gb dedicated memory for the host operating system or some more.

I seem to remember that hd tune got higher scores then native hardware possibly because of a caching mechanism of the host operating system giving the small test pattern of hdtune a boost but it has been a while since i used that setup. I had the disk systems using the default ide emulation.

Can you try the ide mode and see the performance of the guest operating system?

I believe what you're referring to with the caching only occurs with VHDs.

The difference between just the WHS running (7GB left to host) versus all VMs running (1GB left to host) is small but there. I don't think it's a RAM issue though. That's the first HDTune image in my last post.

IDE is the same, and once the ICs are loaded it should be.

 

[MrMike]

I changed the power plan on the host from balanced to high performance and got this in my WHS VM. As usual, it was something simple and stupid.