Hi,
I do agree that zpool remove is a _very_ desirable feature, not doubt about
that.
Here are a couple of thoughts and workarounds, in random order, that might
give us some more perspective:
- My home machine has 4 disks and a big zpool across them. Fine. But what
if a controller fails or worse, a CPU? Right, I need a second machine, if
I'm really honest with myself and serious with my data. Don't laugh, ZFS
on a Solaris server is becoming my mission-critical home storage solution
that is supposed to last beyond CDs and DVDs and other vulnerable media.
So, if I was an enterprise, I'd be willing to keep enough empty LUNs
available to facilitate at least the migration of one or more filesystems
if not complete pools. With a little bit of scripting, this can be done
quite easily and efficiently through zfs send/receive and some LUN
juggling.
If I was an enterprise's server admin and the storage guys wouldn't have
enough space for migrations, I'd be worried.
- We need to avoid customers thinking "Veritas can shrink, ZFS can't". That
is wrong. ZFS _filesystems_ grow and shrink all the time, it's just the
pools below them that can just grow. And Veritas does not even have pools.
People have started to follow a One-pool-to-store-them-all which I think
is not always appropriate. Some alternatives:
- One pool per zone might be a good idea if you want to migrate zones
across systems which then becomes easy through zpool export/import in
a SAN.
- One pool per service level (mirror, RAID-Z2, fast, slow, cheap, expensive)
might be another idea. Keep some cheap mirrored storage handy for your pool
migration needs and you could wiggle your life around zpool remove.
Switching between Mirror, RAID-Z, RAID-Z2 then becomes just a zfs
send/receive pair.
Shrinking a pool requires some more zfs send/receiving and maybe some
scripting, but these are IMHO less painful than living without ZFS'
data integrity and the other joys of ZFS.
Sorry if I'm stating the obvious or stuff that has been discussed before,
but the more I think about zpool remove, the more I think it's a question
of willingness to plan/work/script/provision vs. a real show stopper.
Best regards,
Constantin
P.S.: Now with my big mouth I hope I'll survive a customer confcall next
week with a customer asking for exactly zpool remove :).
--
Constantin Gonzalez Sun Microsystems GmbH, Germany
Platform Technology Group, Client Solutions http://www.sun.de/
Tel.: +49 89/4 60 08-25 91 http://blogs.sun.com/constantin/
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