Comment by stock_toaster
6 years ago
> - Performance is not that great compared to the alternatives.
CoW filesystems do trade performance for data safety. Or did you mean there are other _stable/production_ CoW filesystems with better performance? If so, please do point them out!
XFS on LVM thin pool LV. Stable and performant as far as I can tell.
My terrible experiences with thin pools makes me see btrfs as a pool of wonderful, trouble-free and perfect code.
Just ask yourself what happens when a thin pool runs out of actual, physical disk blocks?
Isn't this a problem for any over provisioned storage pool ? You can avoid that if you want by not over provisioning & checking space consumed by CoW snapshots. Also what does ZFS do if you run out of blocks ?
I have actually managed to run out of blocks on XFS on thin LV and it's an interesting experience. XFS always survoved just fine, but some files basically vanished. Looks like mostly those that were open and being written to at exhaustion time, like for example a mariadb database backing store. Files that were just sitting there were perfectly fine as far as I could tell.
Still, you definitely should never put data on a volume where a pool can be exhausted, without a backup as I don't think there is really a bulletproof way for a filesystem to handle that happening suddenly.
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XFS is not copy on write.
XFS has supported reflinks for some time already, just the deduplication is kind of experimental.
Supporting reflinks is actually more, than can be said about ZoL (see zfsonlinux#405).
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