On 2015-09-17 14:35, Chris Murphy wrote:
The other option (which for some reason I almost never see anyone suggest), is to expose 2 disks to the guest (ideally stored on different filesystems), and do BTRFS raid1 on top of that. In general, this is what I do (except I use LVM for the storage back-end instead of a filesystem) when I have data integrity requirements in the guest. On the other hand of course, most of my VM's are trivial for me to recreate, so I don't often need this and just use DM-RAID via LVm.On Thu, Sep 17, 2015 at 11:56 AM, Gert Menke <g...@menke.ac> wrote:Hi,thank you for your answers! So it seems there are several suboptimal alternatives here... MD+LVM is very close to what I want, but md has no way to cope with silent data corruption. So if I'd want to use a guest filesystem that has no checksums either, I'm out of luck.You can use Btrfs in the guest to get at least notification of SDC. If you want recovery also then that's a bit more challenging. The way this has been done up until ZFS and Btrfs is T10 DIF (PI). There are already checksums on the drive, but this adds more checksums that can be confirmed through the entire storage stack, not just internal to the drive hardware. Another way is to put a conventional fs image on e.g. GlusterFS with checksumming enabled (and at least distributed+replicated filtering). If you do this directly on Btrfs, maybe you can mitigate some of the fragmentation issues with bcache or dmcache; and for persistent snapshotting, use qcow2 to do it instead of Btrfs. You'd use Btrfs snapshots to create a subvolume for doing backups of the images, and then get rid of the Btrfs snapshot.
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