On Friday, 28 July 2023 08:07:10 BST Wols Lists wrote: > On 27/07/2023 17:18, Michael wrote:
> > Any gotchas I should be mindful of? > > If you can run two disks and raid, that's always a good idea. SMART is > supposed to catch disk problems, but they still do die without warning. Yes, esp. SSDs. > btrfs raid is (still) full of gotchas, as far as I know. > > Don't use anything higher than raid-1. Parity raid isn't reliable last I > knew ... I've read some horror stories, but I don't know if the problem was one of bad implementation/recovery, or entirely the fault of the fs. This guy did some comparisons on RAID 5 which worked OK - at least during his experiments: https://unixsheikh.com/articles/battle-testing-zfs-btrfs-and-mdadm-dm.html#btrfs-raid-5 The btrfs docs advice caution: https://btrfs.readthedocs.io/en/latest/btrfs-man5.html#raid56-status-and-recommended-practices > Make sure you know what you're getting. FS people seem to concentrate on > protecting the file system, not the data. I believe btrfs will raid-1 > the metadata without asking if it can, you need to actively ask for the > data to be raided, and that's caught people out not realising btrfs > treats data and metadata differently. (cf the ext3/4 debacle) > > > Your favoured snapshot/backup strategy? > > Manual ... probably shouldn't be. I snapshot / every friday before I do > an emerge on Saturday. /home I ought to snapshot more than I do. I'm also rather reactive and ad hoc with backups. Hence I'm now looking to implement something more systematic. > WATCH YOUR FREE DISK. I think it's all sorted now, but whatever you're > using it was always a good idea not to go over 90% full. For a very long > time, a combination of snapshots and a full disk would wedgie the > system, such that the only way to free up space was to reformat the > entire disk! As I say, I think it's now fixed so you can delete > snapshots, but >90% ain't a good idea anyway > > Cheers, > Wol I've had a /var/ partition on btrfs fill up, because I had forgotten to set up logrotate! No subvolumes or snapshots in there, so deleting some old logs allowed a full recovery with no loss of data. The problem with snapshots is they creep gradually on you as data starts to differ over time and suddenly you could find yourself out of space and potentially out of luck.
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