[CentOS] CentOS 7 and Areca ARC-1883I SAS controller: JBOD or not to JBOD?

Sat Jan 21 17:02:25 UTC 2017
Valeri Galtsev <galtsev at kicp.uchicago.edu>

On Sat, January 21, 2017 12:16 am, Keith Keller wrote:
> On 2017-01-20, Valeri Galtsev <galtsev at kicp.uchicago.edu> wrote:
>> Hm, not certain what process you describe. Most of my controllers are
>> 3ware and LSI, I just pull failed drive (and I know phailed physical
>> drive
>> number), put good in its place and rebuild stars right away.
> I know for sure that LSI's storcli utility supports an identify
> operation, which (if the hardware all cooperates) causes the drive's
> light to blink.  I'm fairly sure I've used this feature on 3ware
> controllers as well.  I use this even when I'm sure of the failed drive
> number and am the only sysadmin for these systems, because I don't even
> trust my own memory.  :)

Yes, that's my attitude exactly. If controller is connected to backplane
correctly, failed (in controller's opinion) drive would have different LED
light lit up (in color, or extra LED depending on backplane). So, just
looking at the box you know which drive to pull. But exactly as you, I am
making sure when rolling out the box into production that I know which
drive has which physical drive number in controller's book, then I know
from controller which drive failed, and which drive's LED expect to shine
when I have my hands on the box, and if it is not what I expect, it will
be long investigation why before I do something. Luckily never happened
that way. Still, as you do, I prefer RAID-6, because even improbable can
happen. Even if RAID10 can give you more speed (which with controller
cache is questionable) I prefer reliability (yes, RAID60 is there too, but
too wasteful for simple things we do).


> This is one reason I prefer RAID6 over RAID5: if you have one failed
> drive in your array, and you pull the wrong one, your RAID5 is now gone,
> but your RAID6 is still functional.  The odds are with you in a RAID10
> but you could get unlucky.  (Not that you want to rebuild two drives at
> the same time but it's still better than losing the array.)
> --keith
> --
> kkeller at wombat.san-francisco.ca.us
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Valeri Galtsev
Sr System Administrator
Department of Astronomy and Astrophysics
Kavli Institute for Cosmological Physics
University of Chicago
Phone: 773-702-4247