From: Derick H Siddoway
Date: April 22 1999 10:36pm
Subject: Re: Ballpark performance.
List-Archive: http://lists.mysql.com/mysql/2270
Message-Id: <0FF7E371FA453450*/c=us/admd=attmail/prmd=amex/o=unresolved/ou=HUB1/ou=AMEX/s=Siddoway/g=Derick/i=H/@MHS>

>Now, I'm curious what sort of HDD subsystem you're using. We're running
>(don't hit me for that) a RAID5 UW SCSI system with 5 HDDs. How much
>performance could I gain setting up a RAID1-0 (striping over mirrors)
>array with 4 HDDs, dedicated for the mysql tree? 


In general, you'll see a small (~25%) increase in read performance,
but a larger (~200%) increase in write performance, for sequential
reads & writes.  For random reads and writes, the increase is less
substantial: ~5% for reads and ~70% for writes.

Big thing to consider, though, is that you'll lose disk space in a
RAID0+1 setup.  Let's assume you have 4 9GB drives.  With RAID5,
you get about 27GB usable, while with RAID0+1, you get only 18GB usable.
Plus, to be safer, you should be running them under some sort of
volume management (more $$) and an extra hot spare (even more $$).

But that cost may be worth it to you.

-- 
derick