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From:Baron Schwartz Date:February 24 2009 1:55pm
Subject:Re: Best RAID for a DB + LVM?
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Hi Waynn,

On Sun, Feb 22, 2009 at 7:46 AM, Waynn Lue <waynnlue@stripped> wrote:
> I currently have a RAID 5 setup for our database server.  Our space is
> running out, so I'm looking to increase the disk space.  Since I'm doing
> that anyway, I decided to re-evaluate our current disk array.  I was told
> that RAID 5 isn't a good choice for databases since it's slower to write.

In theory it is.  It really depends on the controller though.  Some
companies put more effort into optimizing RAID 5 than RAID 10, and the
performance can actually be comparable!  At my last job we used all
Dell servers with PERC6i controllers and RAID 5, and we got a lot of
mileage out of it.  But I have never benchmarked that setup against
RAID 10 on the same controller, because I didn't do benchmarks there,
and now that I'm in a job where I do benchmarks, I've never done it
for anything but RAID 10.

It would be interesting to benchmark the two setups and see.  One
could get a box with 4 disks and configure it one way, then the other,
and run sysbench or iozone or something to see what comes out.

> In addition, I've also been considering setting up LVM to take quick db
> snapshots, after reading various links on the web (and posts to this list).
>
> So on to the questions!  First, if that's what I eventually want to do (get
> a new RAID server with LVM), do I need to do anything special to set up LVM

Not really.  Just use pvcreate, vgcreate and then lvcreate.  Leave
some space unallocated at the last step.  You need some space to
create snapshot volumes.

> on the new system?  Second, what is a good RAID setup for databases?  RAID

Theoretically, for max performance you want RAID 10, and if money is a
concern, well, see if a RAID 5 setup is good enough.

> 10?  0+1?  Third, I have the choice of using SATA or SCSI in conjuction
> with
> the RAID drives I choose.  How much of a difference is there in using SATA
> instead of SCSI, especially in light of whatever RAID I end up going with?

I haven't gotten to benchmark that either, but others posted on that
topic already.

Baron

-- 
Baron Schwartz, Director of Consulting, Percona Inc.
Our Blog: http://www.mysqlperformanceblog.com/
Our Services: http://www.percona.com/services.html
Thread
Best RAID for a DB + LVM?Waynn Lue22 Feb
  • Re: Best RAID for a DB + LVM?Michael Dykman22 Feb
  • Re: Best RAID for a DB + LVM?Andy Smith23 Feb
    • Re: Best RAID for a DB + LVM?Brent Baisley23 Feb
      • Re: Best RAID for a DB + LVM?Aaron Blew24 Feb
  • Re: Best RAID for a DB + LVM?Baron Schwartz24 Feb