Hi

Thank you, unfortunately we bought the DS6800 without PAV feature, so it is not an option for me.

On 15.04.2013 14:53, Staller, Allan wrote:
For traditional z/OS IO, on volumes larger than mod -3  I would prefer PAV 
(either DYNAMIC or HIPER).

IO is queued on the UCB. If the OS thinks the volume is busy, the IO is queued 
without even being attempted, IIRC.

Ignoring the back end of the DASD device, you now have IO that would have been directed 
to 3 (or more)  "actuators" being directed to 1.
This will increase IO queueing.

You *might* be able to get acceptable performance from a mod-9 with some 
judicious dataset placement, (hard to do in the days of SMS).
Anything larger, I would insist on PAV.

Not sure about the IO characteristics of the ZFS.

HTH,
<snip>
We area also around here (i.e. convert 3390-3 or 3390-9 to 3390-27), my 
question is about  the performance.
Our DS6800 has no PAV, but we have a large number multivolume extended ZFS 
datasets.
  From the handling, backup etc,  it would be better to have a 3390-27, but 
from performance point of view ?
</snip>

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