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00733 - USR ASP's again/again
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USR ASP's again/again
Thanks to many answering my initial USR ASP's question. However I have
more. I want to take the question a bit further.
The installation is running an HAS/400 solution, and also they are running
RAID5 on both machines.
I believe this should take care of the discussion about recovery reasons
for implementing ASP's.
Then there are the performance aspect of using ASP's. First of all, if you
have an USR ASP, you will need to have many arms in that ASP to compied
with the number of arms in the System ASP, and very often you don't have
that many. Second, it is true, that if you have USR ASP's and the journal
file is in this, the arm writing the data, will be located the correct
place, and you should expect a performace benefit, BUT in new controller
types, you don't write directly to the arm, you write to the 'non-volative
memory' in the controller, and therefore you don't wait for the disk to
complete the writing process. It is the disk's responsibility to finish the
RAID5 calculation and writing. Of cause, if the controller gets very much
busy, you might expect a delay in the controller, but the newest controller
models do have a big cache, and it will take a lot writing to overload.
Anyone wants to share their thoughts with me?
Regards
Med venlig hilsen,
Erik Rex
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