>> Indeed, but filesystems have worked hard (by carefully ordering writes >> and with the use of journaling) to make sure the "disk" is always in >> a consistent state in the case of a power loss. > Yes, but in this case the filesystem is still considered "unclean" and > needs a (quick) fsck before mounting it.
They may be "unclean" but they're "consistent" in the sense that some tool (presumably included in the `mount` procedure) can/will deterministically and "quickly" bring them to a valid state corresponding to some specific time before the power loss. `fsck` in contrast is a costly tool that that's not only slow but can't provide any guarantees about what's in the end result: it's just making a best effort to guess a consistent state "near" the mess it received. > My point was that LVM actively asks mounted filesystems on LVs that are > snapshotted to bring themselves to a consistent (clean) state before it > does the snapshot. That was (20 year old) news to me. I don't know the details of how that is handled, but I don't think you should presume that it results in a "clean" filesystem. Instead I'd expect a filesystem like ext4 to do something like make sure the on-disk journal covers all changes until "now". === Stefan
