Re: What is a disk arm?

Can you do a test? Try to do a Pwrdwnsys *immed without ending anything
beforehand (if such a thing is safe for the system to do) and time it. It's
not the Worst Case, but it should be a good starting point. I doubt very
much that with 20 arms on a p7 the pwrdwnsys takes that long...
And yes, 1 disk = 1 arm, but beware of virtualization and LUNs and the
like. if those 20 disks are virtual devices on a 400 disk storage, then
it's gonna be faster, if those 20 disks are on a 4 disk raid5, grab a
papyrus, it'll be faster to transcribe the contents...

Best Regards,



On Thu, Jun 13, 2013 at 5:24 PM, Buck Calabro <kc2hiz@xxxxxxxxx> wrote:

It's often said that there's no stupid question, but I think I'm about
to test this adage. I've got my cable set between the UPS and the 720
(8202-E4C). I got the CPI0962 (UPS now attached) message. I don't have
a UPS power handling program written yet, so I want to set QUPSDLYTIM to
a value that will allow the machine to write main store to disk before
crashing. I look at

http://pic.dhe.ibm.com/infocenter/iseries/v7r1m0/index.jsp?topic=%2Frzahr%2Frzahrdlytimco.htm
(Determining the value of QUPSDLYTIM) and I can see that the value is
heavily dependent on the number of disk arms and main storage.
WRKSYSSTS and a calculator tell me I have the 32GB we paid for :-)
WRKDSKSTS tells me I have 8 198C disk units and 12 19B0 disk units. If
that's 20 arms, I'm hosed - the table says it'll take (worst case) 58
minutes to write 32GB RAM to disk (!) [1]

And so, I don't think those 20 disk units equal 20 disk arms but my
Google-fu has failed me in finding a conversion table. I tried Power
720, 8202-E4C, 198C, 19B0. Is 'disk arm' an imaginary unit of measure
like CPW?
--buck

[1] These numbers seem crazy even if worst case. It's really going to
take an hour to write 32GB of data from RAM to disk?
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