Lutz Vieweg <lvml <at> 5t9.de> writes: > > On 06/29/2015 11:35 AM, David Weber wrote: > > we are testing Btrfs as a kvm storage system with > > "defaults,space_cache,nodatacow" mount options and regular snapshots. > > That sounds brave - even with "nodatacow" it appeared to me > that using btrfs with often partially overwritten files like > VM images results in excessively fragmented files. > And taking snapshots kind of counteracts "nodatacow". > > What does "filefrag" tell about your VM images on btrfs? > > (As much as I like btrfs for other purposes, I currently stay > with XFS for VM images, database files and alike.)
Fragmentation can create a performance hit and you have to ponder if the features are worth it. I use Btrfs with regular snapshots on my workstation with Virtualbox since years. Running filefrag on the image doesn't complete after hours but the IO of the VM is still "fast enough". But the definition of "fast enough" can vary heavily. If it becomes to slow I will try a btrfs fi deframent or just recreate the image with a no reflink copy. Cheers, David -- 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
