On Fri, Jun 15, 2018 at 5:33 AM, ein <ein....@gmail.com> wrote: > Hello group, > > does anyone have had any luck with hosting qemu kvm images resided on BTRFS > filesystem while serving > the volume via iSCSI? > > I encouraged some unidentified problem and I am able to replicate it. > Basically the NTFS filesystem > inside RAW image gets corrupted every time when Windows guest boots. What is > weired is that changing > filesystem for ext4 or xfs solves the issue. > > The problem replication looks as follows: > 1) run chkdsk on the guest to make sure the filesystem structure is in good > shape, > 2) shut down the VM via libvirtd, > 3) rsync changes between source and backup image, > 4) generate SHA1 for backup and original and compare it, > 5) try to run guest on the backup image, I was able to boot windows once for > ten times, every time > after reboot NTFS' chkdsk finds problems with filesystem and the VM is unable > to boot again. > > What am I missing? > > VM disk config: > > <disk type='file' device='disk'> > <driver name='qemu' type='raw' cache='none' io='native'/>
cache=none uses O_DIRECT, and that's the source of the issue with VM images on Btrfs. Details are in the list archive. I'm not really sure what you want to use with Windows in this particular case, probably not cache=unsafe though. I'd say give writethrough a shot and see how it affects performance and fixes this problem. -- Chris Murphy -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
