Re: [Qemu-devel] [PATCH] sheepdog: implement direct write semantics

[Liu Yuan]

On 01/09/2013 06:46 PM, Liu Yuan wrote:
> I'll collect some numbers on it.

Well, when I use hdparm -W 0 /dev/vdx to choose the writethrough cache
in the Guest (virtio disk), it says:

address@hidden:~$ sudo hdparm -W 0 /dev/vdb

/dev/vdb:
 setting drive write-caching to 0 (off)
 HDIO_DRIVE_CMD(identify) failed: Inappropriate ioctl for device
 HDIO_DRIVE_CMD(flushcache) failed: Inappropriate ioctl for device
 HDIO_DRIVE_CMD(setcache) failed: Inappropriate ioctl for device
 HDIO_DRIVE_CMD(identify) failed: Inappropriate ioctl for device
 HDIO_DRIVE_CMD(flushcache) failed: Inappropriate ioctl for device
 HDIO_DRIVE_CMD(identify) failed: Inappropriate ioctl for device

Do I need extra flags to enable WCE?

Both Guest and Host kernel is 3.7 and I start QEMU by following command:

$ qemu-system-x86_64 --enable-kvm -drive
file=~/images/test1,if=virtio,cache=writeback -smp 2 -cpu host -m 1024
-drive file=sheepdog:test,if=virtio,cache=writeback

Thanks,
Yuan