Re: Storage array advice anyone?

No. But I am implying that you think very carefully about the amount of data that you read/write to a single disk before you move on to the next disk.

(There are many different terms for this, which is why I chose to describe the mechanics rather than give it a name).

Some people set their systems to 32K per disc at the SAN, then get Oracle to do 1MB direct reads and wonder why things don't work well.

It seems that many suppliers can't go higher than 1MB per disc (at least, whenever I've been on site asking what the maximum is, I've invariably been told that it's 1MB). This means a typical 1MB read will activate two discs - but since many S/As then decide to put a filesystem stripe on top of the SAN stripe, who knows what else can go wrong.

Regards

Jonathan Lewis

http://www.jlcomp.demon.co.uk/faq/ind_faq.html The Co-operative Oracle Users' FAQ

http://www.jlcomp.demon.co.uk/seminar.html Optimising Oracle Seminar - schedule updated Sept 19th

• Original Message ----- From: "Hameed, Amir" <Amir.Hameed_at_xerox.com> To: <jonathan_at_jlcomp.demon.co.uk> Sent: Friday, December 17, 2004 1:37 PM Subject: RE: Storage array advice anyone?

Hi Jonathan,
Are you suggesting that there is no benefit in having a larger stripe width in comparison to a smaller one, for example, 8-way versus 4-way ?

Thanks
-----Original Message-----
From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Jonathan Lewis Sent: Friday, December 17, 2004 4:23 AM
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).

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