IBM E16RMLL-I - Tivoli Storage Manager, Implementation Manual

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Chapter 2. Implementation planning
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It is important to look at the skills available among your staff for a particular
operating system platform. If there are more people familiar with a particular
platform, then it will be easier to maintain Tivoli Storage Manager in this
environment.
2.4.7 Supported devices
There are a wide variety of supported devices on the Windows and UNIX
platforms, including disk drives, tape drives, optical drives, and automated tape
libraries. zSeries and iSeries are more limited in their choice of devices, but
these devices generally have tremendous capacity.
Be careful if choosing a “smaller” platform that you will have the ability to attach
the required amount of devices as the environment grows. On larger platforms
this concern is usually reduced.
2.5 System size
Choosing the correct platform CPU size and memory requirements is an inexact
art. As you would expect, the risk of configuring insufficient resources increases
with the size of the Tivoli Storage Manager implementation. Small Tivoli Storage
Manager implementations are at less risk of choosing an incorrect platform size,
and the incremental cost to scale up or down is small. Many sites start small and
grow into larger systems. However, this is of little help if you are starting large.
The Tivoli Storage Manager server is CPU-intensive, I/O-intensive, and
memory-intensive. CPU is a function of the number of files to manage and how
your platform processes I/O. A large number of small files is more CPU-intensive
than a small number of large files. As the number of files and the amount of data
to be moved increases, each backup, migration, storage pool copy, and
expiration process will use more CPU to maintain the database entries. Tivoli
Storage Manager takes advantage of multiple processors.
In our experience, zSeries platforms seem to be more CPU-intensive than UNIX
platforms. zSeries sites should be aware that Tivoli Storage Manager can use
significant amounts of CPU. We have seen Tivoli Storage Manager among the
top five users of CPU on such systems.
I/O is the major part of Tivoli Storage Manager processing. In fact, Tivoli Storage
Manager does very little else. Backups and restores, database updates and
retrievals, and storage pool management (reclamation, migration, copying) are
all I/O intensive. The I/O subsystem needs to be robust enough to handle this
load. As the number of files and the amount of data climb, the need for a larger,