4 ms·

The #1 point of ZFS is protections again bitrot, ie. checksums on all data. Does bcachefs do this?

lizknope 3y ago
https://bcachefs.org/ https://bcachefs.org/ It's literally the second item listed on the main web site Full data and metadata checksumming
- FullyFunctional 3y ago
  Thanks, that's good news. Unfortunately it seems bcachefs isn't using pools like ZFS but instead, like btrfs, creates file systems directly on a collection of disks. That's a bummer if true.
  - wtallis 3y ago
    What are the use cases where you find micromanaging vdevs worthwhile compared to automatic storage allocation that can be changed and rebalanced later? bcachefs does offer several per-device controls over data placement and redundancy that btrfs lacks; are those still not enough?
    - FullyFunctional 3y ago
      Exactly, I _don't_ want to micromanage devices so I throw them all into a pool (with defined redundancy) and then I allocate file systems and vdevs (for iSCSI) from that. With btrfs (and bcachefs) I have to manually assign devices to file systems and I can't have multiple file systems (well, you can have sub-volumes but you can't avoid a big file system in that collection of devices). Maybe I'm missing something, but the pool abstraction makes this very clean and clear.
      - wtallis 3y ago
        > so I throw them all into a pool (with defined redundancy) and then I allocate file systems and vdevs (for iSCSI) from that. That sounds backwards. Don't you have to manually define the layout of the vdevs first in order to establish the redundancy, and then allocate the volumes you use for filesystems or iSCSI? If you just do a `zpool create` and give it a dozen disks and ask for raidz2, you're just creating a single vdev that's a RAID6 over all the drives. There's an extra step compared to the btrfs workflow, but if you're not using that opportunity to micromanage your array layout I don't see why you'd prefer that extra step to exist. > and I can't have multiple file systems (well, you can have sub-volumes but you can't avoid a big file system in that collection of devices). Isn't this a purely cosmetic complaint? With at least btrfs, you don't even have to mount the root volume, you can simply mount the subvolumes directly wherever you want them and pretty much ignore the existence of the root volume except when provisioning more subvolumes from the root. You can pretend that you do have a ZFS-style pool abstraction, but one that's navigable like a filesystem in the Unix tradition instead of requiring non-standard tooling to inspect.
  - accelbred 3y ago
    If you wan't volume manager features, you can put btrfs/bcachefs on top of LVM
Tuna-Fish 3y ago
bcachefs currently has full metadata and data checksumming, but there is no scrub implementation. This will likely be in the works soon now that it has been merged.

https://bcachefs.org/ https://bcachefs.org/ It's literally the second item listed on the main web site Full data and metadata checksumming

FullyFunctional 3y ago
Thanks, that's good news. Unfortunately it seems bcachefs isn't using pools like ZFS but instead, like btrfs, creates file systems directly on a collection of disks. That's a bummer if true.
- wtallis 3y ago
  What are the use cases where you find micromanaging vdevs worthwhile compared to automatic storage allocation that can be changed and rebalanced later? bcachefs does offer several per-device controls over data placement and redundancy that btrfs lacks; are those still not enough?
  - FullyFunctional 3y ago
    Exactly, I _don't_ want to micromanage devices so I throw them all into a pool (with defined redundancy) and then I allocate file systems and vdevs (for iSCSI) from that. With btrfs (and bcachefs) I have to manually assign devices to file systems and I can't have multiple file systems (well, you can have sub-volumes but you can't avoid a big file system in that collection of devices). Maybe I'm missing something, but the pool abstraction makes this very clean and clear.
    - wtallis 3y ago
      > so I throw them all into a pool (with defined redundancy) and then I allocate file systems and vdevs (for iSCSI) from that. That sounds backwards. Don't you have to manually define the layout of the vdevs first in order to establish the redundancy, and then allocate the volumes you use for filesystems or iSCSI? If you just do a `zpool create` and give it a dozen disks and ask for raidz2, you're just creating a single vdev that's a RAID6 over all the drives. There's an extra step compared to the btrfs workflow, but if you're not using that opportunity to micromanage your array layout I don't see why you'd prefer that extra step to exist. > and I can't have multiple file systems (well, you can have sub-volumes but you can't avoid a big file system in that collection of devices). Isn't this a purely cosmetic complaint? With at least btrfs, you don't even have to mount the root volume, you can simply mount the subvolumes directly wherever you want them and pretty much ignore the existence of the root volume except when provisioning more subvolumes from the root. You can pretend that you do have a ZFS-style pool abstraction, but one that's navigable like a filesystem in the Unix tradition instead of requiring non-standard tooling to inspect.
- accelbred 3y ago
  If you wan't volume manager features, you can put btrfs/bcachefs on top of LVM

Tuna-Fish 3y ago

bcachefs currently has full metadata and data checksumming, but there is no scrub implementation. This will likely be in the works soon now that it has been merged.