VM/CMSPerformance
The IBM S/390 Integrated Server Model B01 will support up to 340 users for a
VM/CMS program development workload.This workload is designed to represent
the VM/CMS end-user community.Workload activities include program input and
editing, compilation, execution, and program test.Each user runs in a separate
virtual machine and enters a variety of CMS and CP commands related to the
activities called scripts. There are 17 such scripts containing these command sets.
The number of users is based on an average think time of approximately 26
seconds between commands and an end-user average response time of 1 second
or less.
While the internal response times achieved by the IBM S/390 Integrated Server are
within the specified limits, other S/390 processors, due to their standard I/O design
point, typically yield lower response times.Since internal response time is one of
several factors that contribute to end user response time, there may be some
instances where end user times are longer than those achieved by other S/390
processors. There are many instances, particularly in remote applications, where
use of the IBM S/390 Integrated Server can eliminate or reduce other time
components to yield net improvement in overall response time.
Again, the capacity of the IBM S/390 Integrated Server is determined by the type of
work being run.One of the key characteristics of the work is I/O content. While the
VM/CMS workload described here contains a relatively light I/O content when
adequate amounts of storage per user are present, paging I/O can become
significant when the number of users is increased beyond a certain threshold.
When paging I/O becomes significant, total I/O can exceed the I/O capability of the
machine and response times will increase.The supported number of users is
determined by the number of users at which either excessive paging occurs or the
S/390 processor becomes saturated.However, with 256MB's of storage for the
P/390 processor, the processor will generally become saturated before excessive
paging occurs.
The maximum number of users supported for a given storage size and think time is
related to the working set size for the average user, which is approximately 90
pages for the VM development workload.Larger working set sizes will generally
support fewer users, and a smaller working set size will allow for a greater number
of users.
The performance data is based on measurements and projections for a basic IBM
S/390 Integrated Server containing a single (RAID5) disk array configured across 4
devices and 1 SSA loop.A customer's actual performance will vary depending on
many factors such as I/O content, system configuration, available storage, and the
specific workload being processed.
VM Guests Performance
VM/ESA supports guests.When running VM guests on the IBM S/390 Integrated
Server, be aware of the following:
Multiple high performance guest support is not provided.Only one guest can
run as V=R, additional guests must run as V=V (the default) with possible
performance degradation.V=F is not supported.This does not affect CMS
guests.
32 S/390  Integrated Server