Storage question

Steve O'Hara-Smith steve at
Wed Sep 9 15:00:08 UTC 2015

On Wed, 9 Sep 2015 09:47:00 -0453.75
"William A. Mahaffey III" <wam at> wrote:

> On 09/09/15 09:04, Steve O'Hara-Smith wrote:
> > On Wed, 9 Sep 2015 08:23:54 -0453.75
> > "William A. Mahaffey III" <wam at> wrote:
> >
> >> I like ZFS in principal (it's one of the things that attracted me to
> >> FreeBSD about a year ago), but, as someone else noted, it seems to
> >> require lots of RAM & possibly CPU for best effect. The MythTV box is
> >> an AMD A4-5000, 1.5 GHz quad-core jaguar, w/ 16 GB of RAM, which isn't
> > 	My house fileserver (erm NAS in modern speak) is a dual core
> > Atom with 4GB. It manages a 4x2TB RAIDZ2 as well as a bunch of jails.
> > According to top it has 2432M for ARC (3592M altogether is wired).
> > Memory is tight but it's not swapping, and it doesn't no matter what
> > the load. Switching to your spec would be a hefty upgrade and would
> > almost certainly make things faster, but then most things can be made
> > faster with an extra expenditure.
> >
> >> especially robusto by today's standards, so I am staying w/ UFS.
> >> Someone
> > 	If you have the opportunity then benchmark ZFS and see, if you
> > can run it the benefits are great.
> >
> I am quite amenable to running ZFS, I just don't want to have to abandon 
> it & return to UFS if my system proves inadequate for the task, hence my 
> caution about it. If I go to ZFS, I (*think* I) use it for the whole 
> drives, except for swap (possibly), & slice it up into 
> 'partitions/slices/whatever' to do the install, right ? That was my 
> take-away from reading the online pages about it. Maybe I need to 
> rethink ....

	Yes that's essentially it - you assemble the raw storage you're
going to use into a zpool from which the storage that backs the filesystems
is drawn automatically. Once you have a zpool making a filesystem is very
cheap. The filesystems share the pool, if you want to cap them you can but
otherwise they're all limited by the pool. I've never filled a ZFS pool, I
don't think I want to.

Steve O'Hara-Smith <steve at>

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