Re: What is a disk arm?

[Charles Wilt <charles.wilt@xxxxxxxxx>]

As I understand it....

Back before my time..disks had multiple independent arms..thus "disk arms"
vs. "disks"

now-a-days, 1 disk = 1 disk arm

Charles


On Thu, Jun 13, 2013 at 4:24 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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