The future of HAMMER1

Rickard von Essen rickard.von.essen at
Fri Jul 20 14:06:46 PDT 2018

Both "scrub of death" and "you have to use ECC ram when you use ZFS" are

One good discussion on the topic can be found on:

On Fri, Jul 20, 2018, 22:37 Predrag Punosevac <punosevac72 at> wrote:

> Hi,
> I was wondering if Matt and the other developers involved can shed some
> light onto the future of HAMMER1 and ultimately of DragonFly.
> I started dicking with DragonFlyBSD 7-8 years ago mostly due to my
> curiosity about HAMMER. I tried few times in the past to use DF as a
> main file server at the place of my employment just quickly to reverse
> back to ZFS and FreeBSD but my home file server is still happily running
> dfly# uname -a
> DragonFly 5.2-RELEASE DragonFly v5.2.2-RELEASE #17:
> dfly# mount
> ROOT on / (hammer, noatime, local)
> devfs on /dev (devfs, nosymfollow, local)
> /dev/serno/B620550018.s1a on /boot (ufs, local)
> /pfs/@@-1:00001 on /var (null, local)
> /pfs/@@-1:00002 on /tmp (null, local)
> /pfs/@@-1:00003 on /home (null, local)
> /pfs/@@-1:00004 on /usr/obj (null, local)
> /pfs/@@-1:00005 on /var/crash (null, local)
> /pfs/@@-1:00006 on /var/tmp (null, local)
> procfs on /proc (procfs, local)
> DATA on /data (hammer, read-only, noatime, local)
> BACKUP on /backup (hammer, noatime, local)
> /dev/serno/5QG00XF0.s1e at DATA on /test-hammer2 (hammer2, local)
> /data/pfs/@@-1:00001 on /data/backups (null, local)
> /data/pfs/@@-1:00002 on /data/nfs (null, NFS exported, local)
> I feel the time to physically rebuild my home file server slowly
> approaching so I would like to be ready for that day.
> In the light of the fact that HAMMER2 is out and recommended for root
> partition does HAMMER have any future? I see Tomohiro Kusumi still
> having a commit or two a month which touches HAMMER but it seems that
> even his commits are minor bug fixes related to his work/poking with
> HAMMER2. Is everyone else done playing with HAMMER1?
> Is HAMMER2 now stable enough to guarantee consistency of my data? My
> concern is that it typically takes at least 10 years for a file system
> to mature under lot of use and abuse by a much wider community than DF.
> BTRFS is vaporware even after major investment since 2007. With the size
> of the DF community I feel it might takes 20-30 years for HAMMER2 to be
> trully safe.
> One of the main advantages for me personally of HAMMER1 over ZFS besides
> fine grained history was that it seems to be ok-ish with non-ECC RAM.
> Scrub of death
> is real thing and I feel very uncomfortable using ZFS on my cheap home
> hardware. I know that under non-budgetary constrains I should use ECC
> memory with DF as well. How safe HAMMER2 is with non-ECC memory?
> Cheers,
> Predrag
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