Posted May 13, 2010 9:03 UTC (Thu) by ringerc (subscriber, #3071)
Parent article: The Next3 filesystem
NTFS snapshots (volume shadow copies) are the one thing I really miss as a Linux server admin. LVM snapshots do *not* cut it for all purposes:
- They require LVM, which has its own issues and isn't always desirable
- They require storage to be reserved for them and allocated to them in advance
- They don't gracefully age out and aren't quietly removed when they run out of backing store. In fact, I recently had a server fail to boot because of an LVM snapshot that'd filled up.
- They need the file system to be capable of being mounted read-only from a dirty state. Not all file systems can handle this.
I find LVM snapshots to be well suited to taking backups, where I need to snapshot a volume, read the snapshot contents, unmount the snapshot and destroy it.
I find them rather less than ideal for when I just want to keep a few snapshots around to provide coarse versioning, as it's so useful for on a Windows server with VSS. An in-filesystem snapshot faclility would be really, really nice for this sort of thing, and one that didn't require loopback mounts (instead providing virtual directory access or the like) would be truly fantastic for backups.