[CentOS] Re: RAID5 or RAID50 for database?

[Ross S. W. Walker]

Hugh E Cruickshank wrote:

> From: Ross S. W. Walker Sent: May 25, 2008 08:56
> > 
> > Typically most vendors recommend a two-prong approach, keep the
> > database data files on a RAID5/RAID6 type array and keep the
> > log files on a RAID10 array.
> > 
> 
> I can not comment on "most vendors" but for the PROGRESS RDBMS RAID5
> is definitely not recommended. It will work but you will see a
> significant reduction in performance. We strongly recommend that our
> clients go with RAID10 (as in RAID 1+0). In-house we only use RAID10.

Ok, most vendors meaning MS, Oracle, Sybase. I am unfamiliar with
PROGRESS (Postgresql variant?), but in my experience with the
aforementioned they typically do all writing to the db log files,
which is recommended to be kept on a RAID10, then when when
transactions are checkpointed, they are written to the DB files.
The software makes all attempts to keep the data written to the
database files as linear as possible to make sequential access
possible and dump/restore fast. This makes the log files
write-mostly and the database files read-mostly and of
course why the two different RAID types.

Of course that really only pays if your databases are large enough
to justify two separate storage systems. Right now my databases
are small enough to be kept together with logs on a RAID10, but
when they grow unwieldy I will move the databases off the RAID10
onto a RAID5/6/50/60 whatever and leave the log files on the
RAID10.

-Ross

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