alt Hacker NewsFrom https://orib.dev/gefs.pdf -
> While snapshot consistency is useful to keep data consistent, disks often fail over time. In order to detect corruption, block pointers contain a hash of the data that they point at. If corrupted data is returned by the underlying storage medium, this is detected via block hashes. And if a programmer error causes the file system to write garbage to disk, this can often be caught early. The corruption is reported, and the damaged data may then be recovered from backups, RAID restoration, or some other means.
Okay! It's got CoW, snapshots, and data checksums. Therefore, it's good enough to compete with ZFS while being way smaller and permissively licensed. Now I just want it ported to Linux and the other BSDs:)
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I don't think it will compete with ZFS or BTRFS (e.g. I don't think ppl will use GEFS over ZFS or BTRFS for a storage server), but it's a modern, much needed FFS replacement.
I've always wondered about similar designs: Doesn't calculating a hash of every block, on every read and every write, create lots of overhead? Why isn't that a problem?
Some systems have dedicated crypto co-processors for confidentiality (encryption) - e.g., I think drives with FDE, and I think Apple Silicon SoCs might have them. Can those be repurposed for hash calculation? What about systems that lack them?
> It's got CoW, snapshots, and data checksums. Therefore, it's good enough to compete with ZFS while being way smaller and permissively licensed.
Does it have a built-in RAID layer? Because if it doesn't, then it can't compete with ZFS in many use cases. For example, what does "data may then be recovered from […] RAID restoration" mean?
With ZFS, if you have a (e.g.) mirrored/RAID-1 configuration, and you fetch some data from one drive and the checksum is wrong, ZFS can check the other drive, and if that checksum is good it can (a) pass the good data up, and (b) use the good data to fix the bad data. Most mirroring systems can't do that both-drives checking: ZFS is self-healing.
(This isn't to say that GEFS won't be useful in many other situations.)