[OpenIndiana-discuss] Zfs stability

Udo Grabowski (IMK) udo.grabowski at kit.edu
Fri Oct 12 20:17:43 UTC 2012

On 10/12/12 09:55 PM, Roel_D wrote:
> Being on the list and reading all ZFS problem and question posts makes me a little scared.
> I have 4 Sun X4140 servers running in the field for 4 years now and they all have ZFS mirrors (2x HD).
 > > They are running Solaris 10 and 1 is running solaris 11. I also 
have some other servers running
 > OI, also with ZFS.
> The Solaris servers N E V E R had any ZFS scrub. I didn't even knew such existed ;-)
> Since it all worked flawless for years now i am a huge Solaris/OI fan.
> But how stable are things nowaday? Does one need to do a scrub? Or a resilver?

A scrub once in a while is recommendable, once a month on a
typical server is sufficient on Sun boxes. You never see any
corruption as long as you don't read the data (which scrub does),
and if, by slim chance, both sides of the mirror are corrupted
at the same data block, and the corruption is hard enough that
the checksum algorithm cannot correct them, then there's this small
chance to loose data.
If you have old Sun boxes, you are generally on the safe side,
our good old seven X4540 are running for years now without having
any serious outage at all, while heavily serving hundreds of
Terabytes of data for our 58 Sun (16 core) blades compute farm
all the time. Never saw something stable and powerful like that,
for such a reasonable price.

> How come i see so much ZFS trouble?

That's just because today OI/Illumos supports much more hardware
than in the good old Sun days when all servers had to go through
a hard qualification process before having a chance to go to market.
Today, everyone can (and is invited to) build it's own server,
but sometimes components and their firmware don't play well (remember
the Intel X25-e SSDs lying about cache flush ? Those were retracted
from the Sun qualified products list before actually sold, we ordered,
but couldn't get one), and having servers with non-ECC memory adds an 
aditional source of trouble. So as welcome as this new variety is,
on the bad side it adds more problems to solve.
Dr.Udo Grabowski    Inst.f.Meteorology a.Climate Research IMK-ASF-SAT
www-imk.fzk.de/asf/sat/grabowski/ www.imk-asf.kit.edu/english/sat.php
KIT - Karlsruhe Institute of Technology            http://www.kit.edu
Postfach 3640,76021 Karlsruhe,Germany  T:(+49)721 608-26026 F:-926026

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