Re: Opinions on Raid

From: Stefan Kaltenbrunner
Subject: Re: Opinions on Raid
Date: ,
Msg-id: 45E43878.5000305@kaltenbrunner.cc
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In response to: Opinions on Raid  ("Joe Uhl")
List: pgsql-performance

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Opinions on Raid  ("Joe Uhl", )
 Re: Opinions on Raid  (Stefan Kaltenbrunner, )
 Re: Opinions on Raid  (Ron, )
  Re: Opinions on Raid  (, )
 Re: Opinions on Raid  (Scott Marlowe, )
  Re: Opinions on Raid  ("Joe Uhl", )
 Re: Opinions on Raid  (Scott Marlowe, )
 Re: Opinions on Raid  (Geoff Tolley, )
  Re: Opinions on Raid  (Arjen van der Meijden, )
   Re: Opinions on Raid  ("Steinar H. Gunderson", )

Joe Uhl wrote:
> We have been running Postgres on a 2U server with 2 disks configured in
> raid 1 for the os and logs and 4 disks configured in raid 10 for the
> data.  I have since been told raid 5 would have been a better option
> given our usage of Dell equipment and the way they handle raid 10.  I
> have just a few general questions about raid with respect to Postgres:
>
> [1] What is the performance penalty of software raid over hardware raid?
>  Is it truly significant?  We will be working with 100s of GB to 1-2 TB
> of data eventually.

this depends a lot on the raidcontroller (whether it has or not BBWC for
example) - for some use-cases softwareraid is actually faster(especially
for seq-io tests).

>
> [2] How do people on this list monitor their hardware raid?  Thus far we
> have used Dell and the only way to easily monitor disk status is to use
> their openmanage application.  Do other controllers offer easier means
> of monitoring individual disks in a raid configuration?  It seems one
> advantage software raid has is the ease of monitoring.

well the answer to that question depends on what you are using for your
network monitoring as a whole as well as your Platform of choice. If you
use say nagios and Linux it makes sense to use a nagios plugin (we do
that here with a unified check script that checks everything from
LSI-MPT based raid cards, over IBMs ServeRAID, HPs Smartarray,LSI
MegaRAID cards and also Linux/Solaris Software RAID).
If you are using another monitoring solution(OpenView, IBM
Directory,...) your solution might look different.


Stefan


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