zfs question

Matthew Seaman m.seaman at infracaninophile.co.uk
Sun Aug 8 12:27:21 UTC 2010

On 08/08/2010 12:43:48, Dick Hoogendijk wrote:
>  Years back I ran FreeBSD, so I have some experience. The last couple of
> years I ran Solaris, followed by Opensolaris. I am very satisfied.
> However, considering the troubles after Oracle took over I have rebuild
> my server system under FreeBSD-8.1 (now running as a virtual machine
> under VirtualBox). All works very well and smooth so I'm going to
> transfer this VM to a real seperate harddisk.
> I have a couple of questions:
> [1] Transfering the VM is best done using dump/restore I guess? (This
> after a smallest creation of fbsd81 on the new harddisk) ?

Yes, that would be a pretty good way of doing your vtophys migration.

> My server has five disks: 1 PATA (160Gb), 2 SATA2 (500Gb) and 2 SATA2
> (1Tb) The fist is disabled at the moment and the others are ZFS mirrors
> under opensolaris. they are not usable for freebsd because the zfs
> versions don't match. I will have to rebuild. ;-)

% zpool list -H -o version zroot
% zfs list -H -o version /

Those are the latest available under 8-STABLE -- 8.1-RELEASE will be the

> However, I'm a bit worried about the status of ZFS on FreeBSD-8.1 I
> don't want my system to boot off ZFS like I have now on OpenSolaris-b134
> I think it is wisest to have the 160Gb IDE drive installed for FreeBSD
> system drive w/ UFS2 and after that create two ZFS mirrors from my SATA
> drives.

Hmmm... well, booting FreeBSD off ZFS works perfectly well.  Apart from
the lack of support in sysinstall, I can't see any good reasons to avoid
it.  However, it's your system, and booting from UFS also works very
well, so do whatever pleases you.

There's more of a question over whether it's a good idea to put swap
onto zfs -- I think the recommendation is still to prefer using a raw
partition or gmirror for that.

> Is ZFS (v14) ready for production on FreeBSD-8.1 and if yes, will I
> still need special settings? The server system is 64bits and has 3Gb
> memory.

Yes.   It works very well.

On amd64 you'll get a pretty reasonable setup out of the box (so to
speak) which will work fine for most purposes.  Of course, if your
system has particularly demanding IO patterns, then you may have to
tweak some loader.conf or sysctl parameters to get the best results.
But that's hardly unique to ZFS.

> I hope to get some answers or good reading points.

The FreeBSD Wiki entries on ZFS are very useful to read:

http://wiki.freebsd.org/ZFS  (and the links from that page)

especially the recipes for installing various different ZFS based
configurations: eg. http://wiki.freebsd.org/RootOnZFS



Dr Matthew J Seaman MA, D.Phil.                   7 Priory Courtyard
                                                  Flat 3
PGP: http://www.infracaninophile.co.uk/pgpkey     Ramsgate
JID: matthew at infracaninophile.co.uk               Kent, CT11 9PW

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