Re: Disk issue

Carley,

  Amazing how the math works out here here just as it should! Let me
explain: Your 6607 drives are 4G units, the 6714's are 17G or just about
4 times larger. Since they contain about 4 times as much of your 'stuff'
than the 4G units and are the same speed they will normally be about 4
times busier. (40% -vs- 10%)

  This is why IBM (and many others) recommend against putting disks of
different sizes in the same ASP. Certainly this cannot be avoided
completely but you skipped one size (8.5G) in between and you can see
the problem it creates. If you were to get the 4G units up to 20% busy
(1/2 of recommended maximum) the 17G units would be around 80% busy!
(Twice recommended maximum).

  Best thing you could do: Replace all of them with 10K RPM 8.5G drives.
OK, That's likely not practical (budget wise) but you may want to add
more arms to off-load those 17's as they are at the recommended maximum
utilization already.  

  Also at V4R4 and up there is a storage pool balance function that can
balance by access that may smooth this out for you some by putting
lesser used data on the 17G drives. (STRASPBAL).

  HTH

    - Larry

"Carley, Neil" wrote:
> 
> Hi,
> 
> Hopefully someone can offer me some advice on this. I have a system here
> (720 V4R3) with 25 disks in the main ASP 18 x 6607's & 7 x 6714's. A couple
> of weeks ago I noticed a few messages in qsysopr reporting problems with the
> disks and recommending contacting service before any serious problems
> occurred, the machine was IPL'd that day and I have not seen any similar
> messages since. Using wrkdsksts I notice that the 6607's are only running at
> about 10% busy whereas the 6714's are running at about 40% busy, is it
> normal to have two different types of disks running like this or could this
> difference be causing a bottleneck on the system as we do tend to push our
> system fairly hard ?

-- 
Larry Bolhuis           | Cogito Ergo Vendo iSeries 
Arbor Solutions, Inc.   |
(616) 451-2500          |               (I think, therefore I buy iSeries.)
(616) 451-2571 -fax     |
lbolhuis@arbsol.com     |        #3  1951-2001
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