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Re: Which RAID level do you use?

From: <lembark_at_wrkhors.com>
Date: Thu, 18 Oct 2001 14:33:19 -0700
Message-ID: <F001.003AF448.20011018142018@fatcity.com>

> I'm interested to hear your recommendations for which RAID level to use with
> Production Oracle databases on Sun Solaris UNIX. My Oracle Performance
> Tuning classroom book clearly recommends RAID 0+1 for file performance and
> data protection, based on an article by Millsap (1996). However, I know of
> at least one other information source (http://www.acnc.com/04_00.html) that
> recommends RAID 5 for databases.
>
>
>
> Which RAID level do you use in Production?

RAID 1 is fine if you have infinite storage (read: Infinite Budget). Try buying an extra TB of disk just for the fun of it and see what your budget committee does to you :-)

Depending on what you are trying to accomplish, RAID 5 works nearly as well for far less disk space. Mirroring will handle a complete failure of some disks without interrupting production; RAID 5 will only keep you from loosing data -- with a heavy performance cost as the hot spare is re-init'd.

There is also an issue of soft- and hardware RAID. I'll assume you would be using hardware for a database server. At that point the O/S sees a bunch of physical "devices" that simply look large. These can be sriped across, etc, using LVM just like any other drives. Net result is that you can plan the hardware failure issues out without necessarly having to deal with all of the LV sizes at the same time.

If you are careful in choosing the stripe size (usually equal to the O/S I/O page size) then there isn't much of a penalty in using RAID 5. Given that most systems use a 4- or 8KB page using 4 x 1KB or 8 x 1KB or 4 x 4KB, etc, works nicely for most situations. Hardware RAID controllers have enough cache that performance usually isn't a problem.

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Received on Thu Oct 18 2001 - 16:33:19 CDT

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