httm VS zfs

My projects and many projects include a THIRD-PARTY-LICENSES.html file when I distribute binaries. See: https://github.com/kimono-koans/httm/blob/master/third_party/LICENSES_THIRD_PARTY.html

The only real advantage I can think of with nested ZFS is that the files in the KVM would obviously be individual inodes in the nested ZFS filesystem and datasets, in addition to the one inode per virtual volume on the hypervisor (or zvol). This would allow for granular file management on the kvm and the use of tools like https://github.com/kimono-koans/httm which is like a command line time machine for ZFS.

> It's worth noting that copy_file_range is used by a lot of things.

Yes, but the trigger feature, block cloning, only landed in the latest 2.2 release. If you immediately hopped on 2.2, and used a system with lots copy_file_range and FICLONE use, yes, you may have a problem (like, as you note, on Gentoo, where this problem surfaced).

Most people were just hopping on the bandwagon. My distro ships 2.1.5, so I have a 6 month wait until this feature lands, so I was just building copy_file_range support into my ZFS apps, right before news of this bug hit.[0]

> There are other things required to trigger the bug that are a lot less common though.

Exactly. My guess is the incidence of this will exceedingly rare for the common user/small NAS user/etc. I've run a corruption detector[0], and what I've found mostly indicates false positives. Some are build artifact fingerprints, which I don't care about, and which were deleted with the next build. The ones with an extant file on another system, I confirmed were a diff match with the origin using `rsync -rincv` and whats on snapshots with `httm --map-aliases`. So far no positive matches.

[0]: https://github.com/kimono-koans/httm

cargo install --git https://github.com/kimono-koans/httm --branch clones strace -f -o stderr.txt -e ioctl -- httm -r -R ~/.zshenv

httm prints the size, date and corresponding locations of available unique versions (deduplicated by modify time and size) of files residing on snapshots, but can also be used interactively to select and restore files, even snapshot mounts by file! httm might change the way you use snapshots (because ZFS/BTRFS/NILFS2 aren't designed for finding for unique file versions) or the Time Machine concept (because httm is very fast!).

All btrfs snapshot tools can have different layouts. It's mostly a nightmare for any one tool to support. Although its not the tool you're looking for, FYI AFAIK httm supports all/most btrfs layouts, but it took more work than necessary to get there.

ZFS only option which requires super user privileges.

[0]: https://github.com/kimono-koans/httm/blob/master/httm.1

httm - Interactive, file-level Time Machine-like tool for ZFS/btrfs/nilfs2

> The only non-junk PCIe3 option that's even advertised here recently is the overpriced WD Red SN700.

Those WD drives seem to have some real issues, at least with ZFS and btrfs. :(

https://github.com/openzfs/zfs/discussions/14793

IMO the "next fs" is just zfs. They somewhat recently merged RAIDZ expansion feature https://github.com/openzfs/zfs/pull/12225 and make regular improvements. If no file system has what you need today, zfs will probably be the first one to have it "tomorrow," imo.

https://github.com/openzfs/zfs/issues/15526#issuecomment-181...

> zpool get all tank | grep bclone

> kc3000 bcloneused 442M

> kc3000 bclonesaved 1.42G

> kc3000 bcloneratio 4.30x

> My understanding is this: If the result is 0 for both bcloneused and bclonesaved then it's safe to say that you don't have silent corruption.

A couple years ago, I had an idea for convincing a filesystem to go faster using 2 compression steps instead of one. I couldn't see why it wouldn't work, and I also couldn't convince myself it should.

It seems to have worked out. [1]

[1] - https://github.com/openzfs/zfs/commit/f375b23c026aec00cc9527...

https://github.com/openzfs/zfs/issues/7631

This is a long-standing issue with zvols which affects overall system stability, and has no real solution as of yet.

TIL. Thank you! https://github.com/openzfs/zfs/pull/15022

Difference may be significant, yes https://github.com/openzfs/zfs/pull/14243