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.

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: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx]
On Behalf Of Matthew Zito
Sent: Thursday, December 16, 2004 12:54 AM
To: Oracle-L
Subject: Re: Storage array advice anyone?

-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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