RE: ASM IO distribution on a SAN

A lot of shops have been striping on top of Symmetrix for years, especially in Oracle environments, using either LVM or Veritas VM to deal with the annoying "lots of 6/8/9 gig disks" traditional symmetrix model. Maybe more people are using metas these days, but the marketing point of ASM was to reduce/remove the need for Veritas in Oracle environments, hence giving Oracle a larger chunk of the per-server revenue.

Basically, it's in Oracle's best interest to commodify the hardware down as much as possible, while reducing the third-party software you need, so that they can shift that money into software revenue for them. Hence, why buy a Symmetrix when ASM can do your RAID for you? Why buy Veritas when ASM will do the same thing? Why buy Sun servers when you can get Dell Linux servers and use RAC for scale? Why buy SRDF when you've got Data Guard? Why buy Quest when you've got AWR/ADDM? Etc., etc.

Back on the technical discussion, the striping of ASM is mostly useless, as other posters have pointed out. But, there is a certain amount of value from a volume expansion/management perspective, as not all filesystems/volume managers/storage arrays elegantly deal with growing and shrinking volumes, so it can be convenient to just throw another disk at the problem and let ASM deal with it.

Thanks,
Matt

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Matthew Zito
Chief Scientist
GridApp Systems
P: 646-452-4090
mzito_at_gridapp.com
http://www.gridapp.com

-----Original Message-----

From: oracle-l-bounce_at_freelists.org on behalf of Baumgartel, Paul Sent: Thu 9/13/2007 11:42 AM
To: oracle-l_at_freelists.org
Subject: RE: ASM IO distribution on a SAN  

I agree. What many people don't realize is that ASM was meant by Oracle to allow small- and medium-size shops, who didn't want to shell out the bucks for a storage system like Symmetrix, to realize the benefits of striping and mirroring. Running ASM on top of RAID gives you stripes on stripes (or what some people call "plaiding"-ugh).  

Having said all that, we run ASM on top of Symmetrix, as it's the standard tier one storage. There are *some* benefits, such as automatic rebalancing, but to my mind it's gilding the lily.  

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http://www.freelists.org/webpage/oracle-l Received on Thu Sep 13 2007 - 12:47:24 CDT