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Re: Hardware vs. Software RAID

From: Mark Brinsmead <>
Date: Sun, 6 May 2007 20:58:43 -0600
Message-ID: <>

Wow. Software RAID. People still use that?

Seriously, its usually not too hard to justify the cost of pushing the RAID logic into the hardware layer.

Software RAID can consume a lot of CPU cycles. And if you happen to be running EE, you've likely paid anywhere from $40K to $90K (depending on features) per CPU to get those cycles. Not wasting CPU cycles on something that is better done in the hardware seems to be a no-brainer in this context.

In addition to saving expensive CPU cycles, hardware raid permits (can permit) the use of write caches. (Caching writes with software raid requires non-volatile memory; specialized hardware.) Hardware RAID can increase the effective transfer rate between the database server and the disks by a factor of 2 or more. And it can be extremely cheap.

Software RAID is (probably) better than no RAID at all. But I would never use it by choice. Nor to save $10k.

If your application is not sufficiently important to warrant the "extra cost" of hardware RAID, how do you justify the "extra cost" of using RAID at all?

Heck, if cost is the primary consideration, you can deploy all the storage you'll ever need (including more than 2000% room for future growth) with a single ATA disk drive costing about $200... Why do I have the feeling that whoever has asked you to cost-justify hardware RAID is next going to demand a cost justification for backups? :-)

Seriously, though, hardware RAID offers numerous benefits. It should be easy to justify. But then, I have seen some pretty strange decision-making processes in my travels...

As for "collateral" to back you up -- why not start with the storage vendor? If they cannot help you justify this purchase, they don't deserve to make the sale!

On 5/3/07, David Peasley <> wrote:
> Hi all,
> I'm being asked to justify the cost of hardware over software raid (38
> gig Oracle database, soon to be migrating to 10g - on Solaris).
> Does anybody know of any good white papers, benchmark tests, etc., that
> you could point me to? Or, any opposing opinions - I can take that
> too. :)
> ...
> --

-- Mark Brinsmead
   Senior DBA,
   The Pythian Group

Received on Sun May 06 2007 - 21:58:43 CDT

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