I just looked at the VM it does not have a cache. That's the default in proxmox to improve performance. On Fri, Dec 7, 2018 at 7:25 AM Austin S. Hemmelgarn <ahferroin7@xxxxxxxxx> wrote: > > On 2018-12-07 01:43, Doni Crosby wrote: > >> This is qemu-kvm? What's the cache mode being used? It's possible the > >> usual write guarantees are thwarted by VM caching. > > Yes it is a proxmox host running the system so it is a qemu vm, I'm > > unsure on the caching situation. > On the note of QEMU and the cache mode, the only cache mode I've seen to > actually cause issues for BTRFS volumes _inside_ a VM is 'cache=unsafe', > but that causes problems for most filesystems, so it's probably not the > issue here. > > OTOH, I've seen issues with most of the cache modes other than > 'cache=writeback' and 'cache=writethrough' when dealing with BTRFS as > the back-end storage on the host system, and most of the time such > issues will manifest as both problems with the volume inside the VM > _and_ the volume the disk images are being stored on.
