On Fri, 20 Jun 2003 09:58:59 -0400, Michael MacIsaac <[EMAIL PROTECTED]>
wrote:
>My two cents:
>
>What would be good to know is the best way to exploit the famed zSeries
I/O
>capabilities. I have questions like:
>- How many PAV "paths" should I use for optimal I/O?
> - What does the IOCDS configuration look like?
>- What has to be done differently on the z/VM user ID?
> - On Linux, does the logical volume still have to be striped?
> - Can I have a non-striped logical volume with PAV and still get an I/O
>performance boost?
>- If so, can the logical volume be extended with vgextend?
>- Can I have a 1TB logical volume with PAV?, 2TB?
>
>Such a HOWTO would be a great resource for the zLinux community!
How many "paths"? Don't know, conceptually I think the more the better (the
max. is 16), but you must watch
out for other limitations like max. number of devices per channel etc. .
In the presentation I gave at WAVV in
Winston Salem ("Linux on zSeries - What's New?" , can be found at
www.linuxvm.org) you find an example
for the IOCDS stuff. The VM guest does not need anything special for PAV.
Striping or not? It depends. What PAV gives you is more subchannels which
can be used simultaneously.
Simultaneous I/O is also one advantage of striping. PAV with striping could
help e.g. in a case like this:
A sequential-I/O-workload and the Base volumes are spread over the ESS
ranks.
Here you could exploit the ressources of the ESS when using striping since
you would
do multiple I/Os into multiple ranks, while w/o striping you would have
multiple I/Os going into one rank.
vgextend extends volume groups and should be possible with a new Base
device.
Adding another Alias requires to deactivate the volume group, do a vgscan,
and reactivate the group.
Klaus Bergmann
