Ceruti, Gerard G wrote:
HI Peter, Ron
I am trying to get a feel if the memory requirements on say a pSeries of
3GB for a SAP APP server would be less on zSeries Linux under zVM, i.e.
the physical would drop to 1 GB with 2GB as swop.
Regards
Gerard Ceruti
may the 'z' be with you
Hello Gerard,
The SAP code is common to all UNIX variants, so the actual Linux SAP
virtual storage requirement will be very similar to that of AIX.
AIX will page-out SAP's virtual memory if the system is short of
physical pages, similarly to z/VM.
The key difference here is that the physical memory under z/VM is being
shared by a number of Guests.
Under AIX your 3GB is only usable by that single AIX system.
You will have to be the judge of how heavily loaded your AIX system is,
and estimate how much of that 3GB of physical memory is sitting idle.
If indeed you consider some physical memory to be idle, then moving to
Linux under z/VM should _technically_ be of benefit,
by being able to share that idle physical memory amongst multiple z/VM
Guests.
But storage is not the only resource to consider, %CPU and its relative
speed is important too.
A large Power5 pSeries system is currently _very_ fast, and until IBM
release their next generation System z,
pSeries _may_ be hard to match.
If your SAP database is already on z/OS, then running SAP on Linux under
z/VM rather than AIX offers other benefits:
1) HIPERSOCKETS - faster Client Server networking
2) Networking all within the same box (security, speed)
3) Reduction in the number of physical computer systems - floor space,
power, cooling etc.
4) Possible common data management - same Sharks, backups etc.
But more often than not, SAP is a business TCO decision made by CIOs,
and not you or I ;-)
mark
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