[CentOS] OT: 3ware [was: Install Centos 6 x86_64 ...]

Mon Sep 8 07:07:53 UTC 2014
Keith Keller <kkeller at wombat.san-francisco.ca.us>

On 2014-09-08, Valeri Galtsev <galtsev at kicp.uchicago.edu> wrote:
> Then you too manage to stick with reliable drives! Performance... well, I
> have array verify scheduled to start 23:00 on Saturday... also, on newer
> controllers you can choose policy with highest priority for IO and lowest
> for rebuild etc. I'm kind of sceptical about extra wear to mechanical
> drives added by RAID check: my drives are always spinning full speed (no
> spin down crap, thank you), and heads are not touching the platters... So,
> I'm not certain there is extra wear. The only wear apart from bearings I
> know about is when arm hits the stopper which only happens when you power
> off the drive, which not the case here too. What do I miss?

I learned the "reliable drive" lesson the hard way, when I accidentally
ordered, and then unwisely decided to use, crappy drives.  Fortunately
no data was ever lost, but the drives made a lot of extra work for me.

You may be 100% correct about wear.  I have no actual evidence that
extra verifies causes more wear than normal use.

For my largest arrays, even if I started at 23:00 on Saturday, it would
still be going through much of Sunday.  Plus I have other disk
operations that occur overnight.  The performance loss isn't terrible
during a verify, but I have noticed it enough that I prefer to avoid it
happening so frequently.

I've heard quite a few horror stories from people who never did a scrub
of their arrays.  But I haven't heard any from people who did scrubs
less frequently than weekly.  Has anyone?  I'm genuinely curious; if
there's a justification for weekly scrubs that's stronger than my fairly
weak justifications for monthly, I'd switch back.


kkeller at wombat.san-francisco.ca.us