DragonFlyBSD Adds HAMMER2 Multi-Volumes Support

[phoronix]

Phoronix: DragonFlyBSD Adds HAMMER2 Multi-Volumes Support

The HAMMER2 file-system that has been used by default on DragonFlyBSD for some time has lacked multi-volumes support compared to its former HAMMER1 file-system. But as of this weekend in the latest Git development code, HAMMER2 now has initial support for multiple volumes...

http://www.phoronix.com/scan.php?pag...2-Multi-Volume

[Steffo]

This filesystem should be ported to other OS like OpenZFS, because the sad thing is, that nobody uses HAMMER2, because nobody uses DragonFlyBSD for serious business.

[Raka555]

This filesystem should be ported to other OS like OpenZFS, because the sad thing is, that nobody uses HAMMER2, because nobody uses DragonFlyBSD for serious business.

I agree. I like what HAMMER2 is, but not going to switch to DFLY just for that.
Then again it might get stuck in limbo like reiser4/5 when someone tries to port it to linux ...

Hardware support is always a problem on non-Windows operating systems.

[uid313]

Is HAMMER2 better or worse than Btrfs and ZFS? Or is it roughly similar?

Could FreeBSD port it to their system? Can it be ported to Linux?
I've heard that DragonFlyBSD have some I/O subsystem changes so maybe it is not so easy to port it to FreeBSD (and Linux?).

[Steffo]

Is HAMMER2 better or worse than Btrfs and ZFS? Or is it roughly similar?

Actually I can't tell. I don't know if anybody can tell, because the filesystem is not available in other OS'.

[skeevy420]

Is HAMMER2 better or worse than Btrfs and ZFS? Or is it roughly similar?

Could FreeBSD port it to their system? Can it be ported to Linux?
I've heard that DragonFlyBSD have some I/O subsystem changes so maybe it is not so easy to port it to FreeBSD (and Linux?).

Feature-wise, it's somewhere in-between ZFS and BTRFS. Hopefully that'll be updated and reflect the past two\three years of changes.

No reason it can't be ported to Linux, in-tree. Unlike ZFS with the CDDL, HAMMER2 uses a modified BSD license and the Linux kernel is full of BSD licensed code. I have no idea how hard it would be, just know that the licenses jive. Personally, if I were IBM Hat I'd have tried to hire Matt Dillon to port HAMMER2 to Linux versus gluing stuff together and calling it Stratis.

[uid313]

Feature-wise, it's somewhere in-between ZFS and BTRFS. Hopefully that'll be updated and reflect the past two\three years of changes.

No reason it can't be ported to Linux, in-tree. Unlike ZFS with the CDDL, HAMMER2 uses a modified BSD license and the Linux kernel is full of BSD licensed code. I have no idea how hard it would be, just know that the licenses jive. Personally, if I were IBM Hat I'd have tried to hire Matt Dillon to port HAMMER2 to Linux versus gluing stuff together and calling it Stratis.

It is not just the license that makes porting feasible or unfeasible but Linux file systems are built on Linux VFS that goes into the Linux block layer and the Linux page cache, and HAMMER2 is built specially for DragonFlyBSD which may look different and have a different architecture with different functions and different APIs.

[ayumu]

I can't help but notice the committer uses a netbsd mail address. There's hope this will eventually translate into a netbsd port.

[skeevy420]

It is not just the license that makes porting feasible or unfeasible but Linux file systems are built on Linux VFS that goes into the Linux block layer and the Linux page cache, and HAMMER2 is built specially for DragonFlyBSD which may look different and have a different architecture with different functions and different APIs.

Yeah, I know. I assume that something like a DragonFlyBSD Porting Layer, like ZFS's SPL, would have to be used to keep HAMMER2 on Linux more 1:1 with what DragonFlyBSD has. But that's all hypothetical. I just know that, legally, it could be done in an in-tree manner unlike ZFS.

[kreijack]

Feature-wise, it's somewhere in-between ZFS and BTRFS. Hopefully that'll be updated and reflect the past two\three years of changes.

Looking at the documentation that you linked, it seems that hammer2 have fewer features than BTRFS and ZFS:
- hammer2 doesn't support replica (RAID1, RAID5...)
- quote support is commented as " scrapped (still possible on a limited basis)"
- in the documentation, I found references to "check code" (that I read as checksum). But I was unable to find any reference to a "scrub" or "resilvering" process

An interesting feature of HAMMER2 that is not available in BTRFS or ZFS is the support for clustering filesystem.

BR
G.Baroncelli