This report analyzes the results observed with Linux guests
running a database server under online transaction processing
(OLTP) workload in a z/VM environment using a relatively large
amount of main memory (80 GB) and then also overcommitting
that memory.
To test the z/VM memory management behavior, the memory was
overcommitted up to a factor of two and the impact of the
following z/VM memory management features were tested:
VM Resource Manager Cooperative Memory Management (VMRMCMM),
initially available with z/VM 5.2 (also known as CMM Version
1)
Collaborative Memory Management Assist (CMMA), initially
available with z/VM 5.3 (also known as CMM Version 2)
These features were expected to improve the overall system
performance in cases where the overall z/VM system is constrained
for real storage.
The paper analyzes the performance of the z/VM virtualization
features when scaling WebSphere Application Server 6.0.2 environments
on an 8-way server.
Each environment is a server triplet consisting of an IBM
HTTP server, a WebSphere application server and a DB2 UDB
database server, where each server resides on an individual
Linux guest. Up to 15 systems are defined running on virtual
hardware provided by one System z. The work load and the number
of server triplets were scaled, which leads finally to an
environment having 2.5x more virtual CPUs than physical CPUs.
