Don,
I dug out these old recommendations from Greg Dyck. Note that he shoots down
my "is 30% a myth idea."
- Individual local page datasets should not exceed 30% (or
25% if you choose) utilization because the contigious slot allocation
algorithm becomes inefficient/unsuccessful for that dataset. The
utilization% at a total paging subsystem level is irrelevent with respect to
the algorithms.
- All local page datasets should be the same size (or close
to it in slots) and device type because of ASMs round robin allocation
algorithm. If one page dataset has 12000 slots and another has 24000 the
utilization% on the second will be about 1/2 of the first.
- Paging bandwidth is as important as paging space.
Converting 9 page datasets to 3 page datasets of triple size will probably
impact performance. More smaller page datasets is always better over fewer
large page datasets.
- A volume should only have a single local page dataset on
it, and no other datasets. Use of WLM managed PAVs by ASM can be used to
eliminate this restriction. Depending on the actual storage subsystem
backing a page dataset it may or may not be reasonable to have multiple
systems using a volume with a page dataset on it.
The archives don't go back further than 2005, but I am sure I recall Greg
had posted several years ago the optimum number of Locals starts at eight.
Ron
> -----Original Message-----
> From: IBM Mainframe Discussion List [mailto:ibm-m...@bama.ua.edu] On
Behalf Of
> Don Williams
> Sent: Wednesday, January 20, 2010 10:40 AM
> To: IBM-MAIN@bama.ua.edu
> Subject: [IBM-MAIN] PAGE datasets -- few large or more small
>
> Another question on page data set sizes...
>
>
>
> We only have 1 DS8000 controller. All volumes are raid 5 and metro
mirrored
> to a second off-site DS8000 controller.
>
> Which configuration is most likely to have the best performance?
>
> Which configuration is most likely to have the best RAS?
>
>
>
> 1. A few large paging volumes (mod-9 or bigger), each with a single
> page data set.
>
> 2. A lot of small paging volumes (mod-3 or smaller) each with a
single
> page data set.
>
> 3. Something in between.
>
>
>
> Don
>
>
>
> Faith is taking the first step, even when you don't see the whole
staircase.
>
>
> -- Martin Luther King Jr.
>
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