ZFS compression?

[Amos]

We're using ZFS on a V440 for our Cyrus spools that are on a 6920 and
all I have to say is KICK A$$!!!  ;-) ZFS will use as much memory as
you can spare for caching, but it hasn't really caused us any
problems. At first it made us nervous because it seemed like all our
free memory disappeared (of course a leak in PAM/saslauthd didn't
help.) However, it has turned out to be fine. And yes, compression is
on. At first I was anxious about that, but it has turned out to be a
total non-issue. So far we've been extremely happy with ZFS.

In fact a short while ago we had a cooling problem with the particular
server room this equipment is in, and to make matters worse the
temperature warning sensor failed us. So the heat got high enough that
things started shutting down on their own, including our Cyrus server.
CRAP! I know for a fact that VxFS would have had to fsck the entire
spools before they would come back. That probably would have taken a
day. If we had to do a restore from tape, oh my that would have been
nasty! However, ZFS came back instantly without the slightest hint of
problems. Things have been running swimmingly (knock on wood) since
then.



On 4/24/07, Vincent Fox <vbfox at ucdavis.edu> wrote:
> Has anyone attempted using ZFS compression on mail spools?
>
> This is a new Cyrus 2.3.8 mail-store, and we are using dual fiber
> HBA to SAN switches and Sun 3510FC units on the backend, multipath
> and active-active on the dual-controllers.  RAID-5 LUNs on each array
> are ZFS mirrored between arrays.  Yes, multiple levels of paranoia.
> We have Sun T2000 which are quad-CPU.  So it seems like there is
> plenty of CPU there for the extra overhead that inline compression is
> likely to add.
>
> Anyhow,  I still envision the I/O being the bottleneck though so I am
> wondering if turning this on will buy me any performance and at what price?
> This system is not in production yet so I am still throwing things at it
> to see at what point it breaks.
>
>
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