Also, Matt Dillon got married; most people don’t work on filesystem commits while on their honeymoon.

ZFS is revolutionary but it still meant for the unmodified Solaris VFS and while there were differences with FreeBSDs VFS, they were manageable.

I may be proved wrong of course, and that would make me very happy ;).

I am curious, why would a port to the other BSDs be inefficient? Wouldn’t this be the case for any other filesystem? I.e. ZFS on FreeBSD has come a very long way from when it was first ported. But its quite ok now after a good bit of work.

I am somewhat concerned that a port to any non-dragonfly OS, will be inefficient and will make hammerfs look bad. Still it would be nice to see it ported to the other BSDs.

The recommendation from Matt was to wait for hammer2.

Porting to OpenBSD will likely be tougher but I agree OpenBSD needs it the most.
I wonder what ever happened to the GSoC effort: perhaps it was not desired effect but OpenBSD tends to keep those projects closed, or perhaps the student dropped the ball completely before starting.

https://www.dragonflydigest.com/2013/06/27/12033.html

Deduplication is also available and works very well:

https://www.dragonflydigest.com/2013/08/28/12369.html

Kraileth – the person who was working on that Hammer2 port got a job offer too good to refuse right at the start of the GSoC period – and also too much to work on both projects at once, unfortunately.

Thanks for considering some serious port, tkusumi! You definitely won’t have a lack of volunteers to help test this. If you start this project, please use some means of communicating progress and keeping people informed. Too many interesting projects unnecessarily die a silent and lonesome death.

BTW: Does anybody have any information about how the GSOC project around porting HAMMER(v2) went? It was announced on Undeadly once – only to never be heared from again… Even if the project did not succeed it would have been nice to know a bit of the background (how far did it get? what where the problems? etc…)

The initial target will be what dillon (Matt Dillon) has done on DragonFly by 2009 or so. There are some other features added by other devs in 2009-2011 time frame, but these are either not enabled by default, or incomplete, or unstable. It also has some design issues because no such thing was initially designed to be implemented. People are basically only using HAMMER code written by Matt, so ignoring the rest won’t be a problem anyway.

Technically speaking the VFS difference obviously is difficulty of porting any filesystem (not specific to HAMMER). As far as I know Matt has rewritten namei, and some incompatibility in VOP operations compared to FreeBSD. It also has a large filesystem buffer, plus there is an idea of “layers” within a buffer which is used by HAMMER. These are something that may or may not be an issue on porting HAMMER.

Locking probably needs to be rewritten or reconsidered since lwkt tokens in DragonFly behaves quite differently from ordinary kernel mutex as well as design difference from OpenBSD kernel.

tkusumi, how do you see the timing/planning of the HAMMER port? And you are confident that you will be able to complete the port? I would really look forward to it, and many other users as well.

“..Dragonfly has HAMMER (TMC as well), but it looks pretty cool. Somebody should totally port it.”

Any kernel fs more or less relies on vfs and/or page cache interface that kernel has, but people somehow (try to) port them whether that’s ntfs or xfs or reiserfs.

I respect the “I’ll do it because I like the challenge” approach, but it’s a real project that provides real value and I think that’s worth real money. :)