RAID-5 and database servers

Eric Rostetter rostetter at mail.utexas.edu
Thu Mar 11 13:36:21 CST 2010


Quoting "J. Epperson" <Dell at epperson.homelinux.net>:

> On Thu, March 11, 2010 11:17, Dan Pritts wrote:
>> On Tue, Mar 09, 2010 at 04:54:44PM -0600, John G. Heim wrote:
>>> Has anyone configured a database server with RAID-5? Is it really a bad
>>> idea
>>
>> http://www.orafaq.com/wiki/RAID
>>
>
> Which says that unless money is no object, go with RAID 5.

I'd say the page is somewhat outdated.  If your disks are large,
and most disks are today, RAID 5 should be replaced by RAID 6 or better.
RAID 5 is risky if your disks are large...  The larger the disk, the better
the chance of a second failure during a RAID 5 rebuild (causing a total lose
of data).

Also, while it does indeed say go with RAID 5 if you can't afford RAID 10,
it also says:

> use where availability is important, AND 'read' will be the majority of I/O's

If your database is mostly write, RAID 5 would not be a great idea...

Fortunately most databases are either mostly read, or mixed read-write.
But there are some mostly-write databases, and these would be a bad fit
for RAID 5 (or RAID 6).

Again, it depends on your environment and your needs... It is possible RAID 5
is perfect for your needs, but terrible for my needs...

If you don't need fast access, then it doesn't matter... Some people have
databases, and it takes many hours to generate a report, and they are okay
with that.  Others can't bear it if the report takes more than 30 seconds...
If your database use is interactive and response time is important, you
likely need a different setup than if your database is mostly batch
oriented and response time isn't as important...

-- 
Eric Rostetter
The Department of Physics
The University of Texas at Austin

Go Longhorns!



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