RE: Storage array advice anyone?

        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 [mailto:jonathan@xxxxxxxxxxxxxxxxxx] 
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.

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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