Hi Martin,
Martin wrote:
I agree for non enterprise users the expansion of
raidz vdevs is a critical missing feature.
Now you've got me curious. I'm not trying to be inflammatory here, but how is
online expansion a non-enterprise feature? From my perspective, enterprise
users are the ones most likely to keep legacy filesystems for extended lengths
of time, well past any rational usage plan. Enterprise users are also the ones
most likely to need 24/7 availability. Any hacker-in-a-basement can take a
storage pool offline to expand or contract it, while enterprise users lack this
luxury.
Not exactly. All users would lack the ability to expand a raidz dev
(which in turn could require resilvering so it comes with lots of other
Enterprise feature questions), but it's possible now to expand a pool
containing raidz devs-- and this is the more likely case with enterprise
users:
# ls -lh /var/tmp/fakedisk/
total 1229568
-rw------T 1 root root 100M Jan 9 20:22 disk1
-rw------T 1 root root 100M Jan 9 20:22 disk2
-rw------T 1 root root 100M Jan 9 20:22 disk3
-rw------T 1 root root 100M Jan 9 20:22 disk4
-rw------T 1 root root 100M Jan 9 20:22 disk5
-rw------T 1 root root 100M Jan 9 20:22 disk6
# zpool create test raidz /var/tmp/fakedisk/disk1 /var/tmp/fakedisk/disk2
/var/tmp/fakedisk/disk3
# zpool list test
NAME SIZE USED AVAIL CAP HEALTH ALTROOT
test 286M 155K 286M 0% ONLINE -
# zpool add test raidz /var/tmp/fakedisk/disk4 /var/tmp/fakedisk/disk5 /var/tmp/fakedisk/disk6
# zpool list test
NAME SIZE USED AVAIL CAP HEALTH ALTROOT
test 572M 159K 572M 0% ONLINE -
Otherwise, you're absolutely correct. I think some enterprise users
would probably like to have the ability to expand/contract even raidz
groups. I'm sure it's possible to implement this, and luckily ZFS was
designed with the ability to add these features over the course of
time. Still, it's better to get ZFS out and in use sooner rather than
later, right?
Experience taught me that enterprise users most need future flexibility and
zero downtime.
With respect to expanding a pool based on raidz vdevs (and definitely
with respect to expanding a filesystem), that's available today, with
the limitation that you can't expand a raidz group itself.
Regards,
- Matt
--
Matt Ingenthron - Web Infrastructure Solutions Architect
Sun Microsystems, Inc. - Client Solutions, Systems Practice
http://blogs.sun.com/mingenthron/
email: [EMAIL PROTECTED] Phone: 310-242-6439
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