When and why to deprecate filesystems [LWN.net]

When and why to deprecate filesystems

Posted Mar 8, 2022 18:16 UTC (Tue) by smurf (subscriber, #17840)
In reply to: When and why to deprecate filesystems by Wol
Parent article: When and why to deprecate filesystems

You can do the same thing with btrfs snapshots. Way faster than rsync because it doesn't have to scan a complete hierarchy only to discover that nothing has changed.

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When and why to deprecate filesystems

Posted Mar 8, 2022 23:10 UTC (Tue) by Wol (subscriber, #4433) [Link] (3 responses)

???

How does btrfs snapshot magic everything onto a different hard drive?

And to the best of my knowledge, btrfs raid-5 is still in experimental eat-your-data status ...

I use lvm on my live raid-5 array to take live snapshots, and lvm/rsync on my backup drive to take full/incremental backups.

Cheers,
Wol

When and why to deprecate filesystems

Posted Mar 9, 2022 6:08 UTC (Wed) by calumapplepie (guest, #143655) [Link]

https://btrfs.wiki.kernel.org/index.php/Incremental_Backup

When and why to deprecate filesystems

Posted Mar 10, 2022 2:31 UTC (Thu) by bartoc (guest, #124262) [Link] (1 responses)

btrfs raid5 is arguably less "eat your data" than lvm raid5, since it does actually checksum and can, in fact, detect when drives are doing bogus stuff. You need to be quite careful with scrubbing regularly (and per drive) and with what you do if you need to rebuild the array. I don't really recommend running raid5/6 in any system using SATA drives, they are too willing to lie to you and try and cover up impending failures.

Tbh ZFS' raid5 also leaves something to be desired since it avoids the write hole by doing things that can have pretty bad performance consequences down the line (esp with how unwilling ZFS is to muck around with stuff on disk, in general). I'm hoping bcachefs' approach pays off (it does raid5 by initially writing the data in raid10 (or at least mirrored), committing that, then later rewriting that mirror to raid5 and atomically updating the filesystem metadata once it's done.

When and why to deprecate filesystems

Posted Mar 14, 2022 15:10 UTC (Mon) by hkario (subscriber, #94864) [Link]

btrfs raid5 is still marked as experimental, while yes, HDDs lying about their ability to read valid data is an issue, that can be fixed by placing dm-integrtiy below MD-raid and then RAID-5 works fine

also, HDDs lying about bad sectors is not only a RAID-5 issue, it's just as likely to impact RAID-1 setups