Theoretically, if the activity of the database doesn't involve "too much"
disk writing, and the cache is "large enough", etc., etc., you can use
parity.  When disk drives cost a lot of money, there was some justification
for it.  Now that drives are cheap, there really is no justification.  To
cripple the processing power of an E15K in order to save some money on hard
drives really is a case of being penny wise and dollar foolish.  You would
probably be better off buying a less powerful computer and using the savings
to increase the drive count.

The performance of the RAID 5 systems at my shop here is terrible.

Remember the story of that Sparc 4500?  (Actually, now that I think about
it, I think it was a 4000.)  Well, that box was for the test lab.  The
production box was 10 CPU's of an E10K with an EMC tower.  (I have forgotten
the CPU speed -- probably either 250 Mhz or 300 Mhz.)  The 4000 had 4 Gb
RAM, the production box 6 Gb.  The production box was set up by Oracle
consultants to be completely OFA compliant.  At this time, EMC was still
using RAID-S (Uh-oh).  The same 80 Gb cesspool of a database was put on both
boxes.  On the production box, the Oracle consultants along with the EMC
people worked to distribute the database I/O over the drives in the EMC
tower.  On the test box, the entire database and all the Oracle binaries
were dumped on the big mirrored stripe.  When the testers ran the
benchmarks, the test box was processing transactions at THREE TIMES rate of
the production box.

Feel free to correct me if I am wrong, but I think, now that drives are
cheap, EMC no longer uses RAID-S.

I suppose, in certain circumstances, a RAID 5 arrangement might work OK.
But, in every case that I have seen, it's performance has always sucked the
moose.


> -----Original Message-----
> 
> 
> Fortunately my SA believes that so we were able to present a 
> united front at
> the presentation (and yes, the Sun rep said that with a large 
> enough cache
> RAID 5 works just as well as 1+0 - which is what we would be using).
> 
> 
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Author: Stephen Lee
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