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Bcachefs may be headed out of the kernel

(lwn.net)
144 points ksec | 3 comments | 04 Jul 25 13:32 UTC | HN request time: 0.823s | source
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msgodel ◴[04 Jul 25 17:53 UTC] No.44466535[source]▶
The older I get the more I feel like anything other than the ExtantFS family is just silly.

The filesystem should do files, if you want something more complex do it in userspace. We even have FUSE if you want to use the Filesystem API with your crazy network database thing.

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heavyset_go ◴[04 Jul 25 19:44 UTC] No.44467306[source]▶
Transparent compression, checksumming, copy-on-write, snapshots and virtual subvolumes should be considered the minimum default feature set for new OS installations in TYOOL 2025.

You get that with APFS by default on macOS these days and those features come for free in btrfs, some in XFS, etc on Linux.

replies(1): >>44467710 #
riobard ◴[04 Jul 25 20:40 UTC] No.44467710[source]▶
APFS checksums only fs metadata not user data which is a pita. Presumably because APFS is used on single drive systems and there’s no redundancy to recover from anyway. Still, not ideal.
replies(1): >>44467765 #
vbezhenar ◴[04 Jul 25 20:47 UTC] No.44467765[source]▶
Apple trusts their hardware to do their own checksums properly. Modern SSD uses checksums and parity codes for blocks. SATA/NVMe include checksums for protocol frames. The only unreliable component is RAM, but FS checksums can't help here, because RAM bit likely will be flipped before checksum is calculated or after checksum is verified.
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1. londons_explore ◴[04 Jul 25 21:49 UTC] No.44468119[source]▶
Most SSD's can't be trusted to maintain proper data ordering in the case of a sudden power off.

That makes checksums and journals of only marginal usefulness.

I wish some review website would have a robot plug and unplug the power cable in a test rig for a few weeks and rate which SSD manufacturers are robust to this stuff.

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2. Quekid5 ◴[05 Jul 25 15:03 UTC] No.44473240[source]▶
I'd say it makes checksums even more important so that you know whether something got corrupted immediately and not after a year (or whatever) has gone by and you actually need it.
replies(1): >>44476116 #
3. londons_explore ◴[05 Jul 25 22:32 UTC] No.44476116[source]▶
The problem is that if the SSD suffers a power failure and reverts a 1 megabyte block of metadata to the way it was yesterday, the filesystem won't see that as corruption - since all the checksums will match.

Yet all the pointers in that metadata will point to data which no longer exists, and your filesystem will be destroyed.