Il 09/01/2013 11:58, Liu Yuan ha scritto: > 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: > > test@vm1:~$ 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?
"hdparm" is specific for IDE devices. sysfs is supported by SCSI (including IDE with libata, and virtio-scsi) and virtio-blk. You can use this for SCSI: echo 'write back' > /sys/block/sda/device/scsi_disk/*/cache_type and a similar command for virtio-blk. Paolo > 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 > >
