Summary: Will Battery Backup Speed up Raid Set.
From: Ron Bramblett (bramblet_at_fuller.com)
Date: 09/13/04
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Date: Mon, 13 Sep 2004 08:59:05 -0500 To: Unix Managers <tru64-unix-managers@ornl.gov>
Hello,
My original question
Just curious basically.
I have a AS2000 with 2 300Mhz CPU's, 4-member raid 5 set on KZPSC-BA. 512MB
memory
I bought a KZPSC-UB battery backup and was wondering what I can check before I
install it and then again after to see the difference.
Has anyone done this before? I know how to do it, I was just wondering if it
will help in any forseeable way.
Answers from
rob.leadbeater
It probably will speed it up for some operations.
With the battery installed, then the write cache functions of the card
can/will be enabled, so you should see a performance gain when writing.
Jeffrey_Hummel
If the battery is working you should be able to set up a write-behind
cache. I'm not sure what messages will tell you if it is really working.
"Fred N. van Kempen"
Yes, because it will enable the "Delayed Write-Back Cache", which
vastly improves the speed on disk *write* operations.
Selden E Ball Jr
The battery backup is for when your RAID subsystem loses power for whatever
reason. It won't make any difference in performance.
"Maaskant, Gert"
Yes you can...
You can enable write back cache, that makes the writes mutch faster. The KZP
controller told UNIX that the writes are done, bud in real life is isn't.
It's difficult how to monitor, before and after. Because the write time are
not real counters.(After install)
I installed the battery over the weekend. And haven't seen any results yet.
My error (write-back cache was already installed)
I tested it by filling up one partition of the System disk with multiple files
and then when nothing was going on, I wrote a script to copy the files to the
raid set. I timed this operation
I then tested it after I got the battery installed. Same script as above. The
first one took 9 minutes 13 seconds and the second one took 9 minutes 15
seconds
But thinking about this now, if I would have had the battery installed on
August 20th, I could probably have gotten by without reinitializing the raid
set and copying the data from tape back to it.
That would have saved me 4 or 5 hours and they could have had the system
around noon on Friday instead of noon on Sat.
Thanks everyone.
-- Ron Bramblett Fuller Brush Company Systems Adminstrator Almost 100 years strong and still going ...
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