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Two different environments are targeted in this chapter, one being the larger Domino workloads with one server serving thousands of users, and the other being an environment with many smaller servers. Both of these environments can run under z/VM on a zSeries processor.
A one-guest system incurs the overhead of VM without its benefit of being able to optimize resources for multiple guests. If you are not running other work, you should consider running Linux natively for a single Domino server. The native LPAR environment was not evaluated from a performance or capacity planning perspective, since the resources in that environment are dedicated so the capacity planning functions would be the same as in an xSeries® or pSeries® environment.
On the other hand, since Domino is a 3-bit application with an addressing limit of 2 GB, the storage management capabilities of z/VM can allow multiple Domino servers to run in a single system.
For experimentation purposes, three Linux servers were used during the project, with different configurations used to show specific points of interest:
LinuxA supported one Domino server, and was used for experiments running between 300 and 1500 users. The DASD for LinuxA was ESS on FICON™ channels.
LinuxB supported one Domino server, and ran 400 users. The DASD for LinuxB was RVA on ESCON® channels.
LinuxC supported two Domino servers, each supporting 400 users. DASD for LinuxC was mixed.
The purpose of the different environments was to test memory constraints, understand DASD performance issues, and determine any side effects of running servers together. All of the tests were performed using two virtual processors backed by two real processors. Thus, each Linux server had two virtual processors defined.
We ran one test workload with just one virtual processor; it had very poor performance. We did not research this, because Domino runs best with two or more processors available.
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