On Saturday 01 November 2008, Nicolas Martyanoff wrote:
> I'm thinking about switching my main desktop to FreeBSD for various
> reasons (main one, I love it on my laptop and server), and I've been
> considering using ZFS. I'd like to have a disk-modular system, ie.:
>
> - Being able to have mirroring.
> - Being able to add new disks without effort.
> - Being able to add new disks AND mirroring disks (spare disks ?) at
> the same time.
>
> I'm gonna begin with 2x 1TB disks with mirroring, and I'd like to be
> able to add, if needed, new disks, for example 2x 1.5TB to get 2.5TB
> diskspace fully mirrored. The whole process shouldn't need to reinstall
> the system, or to change the slice/partition layout, ie. be totally
> transparent for the data.
> And for this particular need, ZFS seems to be the way to go.


I'm happily using ZFS on a 32-bit FreeBSD desktop system (that also plays a
home server role). It should meet your disk-modularity requirements above,
with the exception that it's not possible to add disks to a raidZ set
(though it is possible to add additional sets to the same zpool).

> However, I'm a bit worried about FreeBSD's ZFS implementation:
>
> - I've got a 64bits dual core 2GHz CPU, but can't use an amd64 FreeBSD
> since Xen, NVidia drivers and wine don't work on it; but ZFS is said
> to be unsuitable for i386.


That's overstating the case. The extra memory headroom on amd64 may make
things simpler, but it's certianly possible to run ZFS on FreeBSD i386 as
long as you have a couple gigs of RAM (I actually only have 1.5 GB) and
follow the tuning guidelines. You should also be willing to monitor your
system and go through one or two fine-tuning cycles

> - It's said you can't boot from a ZFS pool.


There are patches available to allow this but frankly I don't see the
appeal. I think it makes much more sense to have / (including /boot) be a
regular UFS2 filesystem on a small partition. If something goes wrong you
can boot from a CD or single-user and not have to worry about getting your
ZFS pools back online before you can even start troubleshooting the system.
Since (unlike Solaris) FreeBSD doesn't force you to dedicate whole disks to
ZFS, this is a viable option. As Miroslav mentioned you can make a small
root partition on two disks and set them up as a gmirror, leaving the
remainder of the disks available for your zpool(s).

> So could you please tell me if using ZFS is ok for me, or should I use
> a gmirror system (but I don't think I can easily add new disks to this).


You could get most if not all of what you're after with gmirror, gvirstor,
gjournal, etc but it sounds like ZFS is really what you're after and I
think you'll be fine. I haven't actually added any disks to my setup since
I switched to ZFS but it's nice knowing that I can. Add to that cheap
snapshots, checksumming and self-healing and easy administration and I tink
it's an easy sale.

JN
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