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RE: Storage array advice anyone?

From: Johnson, George <GJohnson_at_GAM.COM>
Date: Fri, 17 Dec 2004 11:45:26 -0000
Message-ID: <>

        So would you say that "storage virtualisation" is this another gimmick from the marketing dept of the storage manufacturers, being used to pull the wool over our eyes, to shift units?

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

From: Jonathan Lewis [] Sent: 17 Dec 2004 9:23
To: Oracle-L
Subject: Re: Storage array advice anyone?     

Sorry to come in so late on this one - I've had a busy three months, and only just got back to reading the mail.

Personally I find the whole 'virtualization' thing a complete con-trick.

Sure, I now have a LUN which is really 50 different spindles - so what good is that if I send a 'single read request' and that activates eight of them. It only takes 8 requests like that and there are 64 reads queued up somewhere, and who knows where they might be ? Ask Cary Millsap about queueing and unstable response times. (Then ask Stephen Barr what the minimum and maximum response times were for his Parallel Query problem).

And another thought - I've got a LUN which has 50 different spindles. Using reasonably modern discs, that's probably around 4TB of spindles. How many other databases are going to hitting those spindles ? That's what I asked the DBA's at a site recently when there 56GB database was on a 4TB SAN. Their S/A was insisting that the SAN has no performance issues - the database had recorded its first 3-second 'db file sequential read' time just fifteen minutes after I reset the wait times.


Jonathan Lewis The Co-operative Oracle Users' FAQ Optimising Oracle Seminar - schedule updated Sept 19th

-Virtualization/abstraction of storage objects - when the LUN you are
sending I/Os to is comprised of chunks from 50 different spindles from 10 different RAID-5 groups, the performance is excellent.


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-- Received on Fri Dec 17 2004 - 05:41:03 CST

Original text of this message