Disk performance crippled using virtio disk

[cosmos]

I set up a VM for 2k12r2. The disk is a sparse raw file, converted from a .vhdx snapshot taken with disk2vhd.

The configuration of the system, with the disk connected to ide0 was as follows:

agent: 1
balloon: 2048
boot: cd
bootdisk: ide0
cores: 2
hotplug: usb
ide0: local:102/vm-102-disk-2.raw,cache=writethrough,size=953866M
ide2: local:iso/Hiren's.BootCD.15.2.iso,media=cdrom,size=609268K
memory: 4096
name: helios
net1: virtio=86:7F:49:66:6E:DD,bridge=vmbr0,firewall=1
numa: 1
ostype: win8
smbios1: uuid=cc17d05d-99cb-42fb-9541-a8f448604bd6
sockets: 1

After starting up the maching and installing virtio net, disk and balloon (taken from 0.1.118), it was time to connect the raw file to a virtio controller. Which I did.

To my despair, the system crawled! It took around 3 minutes for the 2k12 server manager window to come up. I reversed the disk and connected it back to ide0. The system booted up in seconds and the server managed window popped up in less than 30"!

Note that in both cases (either ide0 or virtio0) write-through is enabled.

What could be wrong here? The virtio controller is supposed to be blazing fast, compared to ide.

 

[spirit]

do you have tried the stable driver ? (0.1.102)
https://fedorapeople.org/groups/virt/virtio-win/direct-downloads/stable-virtio/virtio-win.iso

Also, use cache=none , you'll have pretty slow write with writethrough. (fsync at each write)

 

[cosmos]

Still shouldn't virtio writethrough outperform ide writethrough? And, as for 0.1.102, I did not use that because I saw a lot of comments regarding bug fixes and enhancement on the windows 2k12 driver.

I don't think that I will see any change though, it's just inexplicable for me.

 

[cosmos]

Ok, this is driving me crazy. Now the system behaves as bad as it did with virtio. But I did have excellent boot times with ide!

Will keep testing, perhaps I'll be able to find something...