Re: how about ram_based ssd compare to high_class disk array such as emc dmx 800?

From: Jonathan Lewis <jonathan_at_jlcomp.demon.co.uk>
Date: Wed, 27 Feb 2008 20:58:46 -0000
Message-ID: <co2dndl21oxiU1jaRVnytAA@bt.com>

<gzsunnyyao_at_hotmail.com> wrote in message news:6de3bfac-b9b3-4b0c-a968-8551ffcb32d9_at_q78g2000hsh.googlegroups.com...
> my system include oracle rac (2 hp super dome 24cpu 40G mem , 1
> EMC DMX 800),
> I wish to fix the io bottle_neck, can I use ram_based ssd such as
> ramsan for redo file to resolve the problem, how about ram_based
> ssd compare to high_class disk array such as emc dmx 800?

There are two problems with that question.

First, what type (and scale) of problem do you think you have with the redo log that means it's the only thing that can be addressed to resolve your performance problems.

Secondly, if the redo log is a critical sticking point, it may be CPU starvation that is more significant than the simple write speed - especially if you have set your SAN to have a write-only cache for the redo log.

See Kevin Closson's blog for various discussions about the log writer: http://kevinclosson.wordpress.com/ Search for SSD or LGWR

-- 
Regards

Jonathan Lewis
http://jonathanlewis.wordpress.com

Author: Cost Based Oracle: Fundamentals
http://www.jlcomp.demon.co.uk/cbo_book/ind_book.html

The Co-operative Oracle Users' FAQ
http://www.jlcomp.demon.co.uk/faq/ind_faq.html
Received on Wed Feb 27 2008 - 14:58:46 CST

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