Chapter 3. zSeries and Linux 29
3.2.2 Systems management functions built-in to z/VM
There are many built-in systems management functions in z/VM. We describe just a few of
Customers wanting to exercise command and control over their ‘real’ discrete server farms
typically have to purchase additional servers to run
Command and Control software products,
often times also requiring client code to be installed on each server image being managed.
This can become expensive in terms of software licence fees (for the servers and client code)
plus additional hardware and networking expenses for the servers, not to mention the added
complexity. z/VM includes a lot of
Command and Control function built into the product.
Resource utilization controls include the ability to allocate processor capacity on a per-image
basis with a high degree of granularity. Adding more resources like memory, disk space, and
data-in-memory support can be done quickly and easily, though sometimes requiring a
re-boot of the affected Linux images depending on the resource being added.
VM offers tools like REXX, the Programmable Operator (PROP) and Pipelines, to build
automation routines that can help minimize the manual intervention required to manage a
server farm. For example, you could capture console traffic from Linux servers and
programmatically perform system operations based on the console data.
3.3 Consolidation and scalability
In this section we explain the advantages that z/VM offers when you need to grow the
capacity of your solution (scalability) or make more efficient use of disparate server resources
The zSeries platform has long been recognized for its ability to scale to support the
consolidation of diverse workloads. Processors and disks (such as the Enterprise Storage
Server) can be incrementally upgraded to meet growing demands. Once upgraded, the
zSeries server can then scale or grow its Linux workload in two ways.
Vertical growth - when more system resources are added to an existing Linux image. For
example, a Linux virtual machine could be given more processor capacity, more virtual
memory, more I/O devices, or more virtual networking bandwidth.
Horizontal growth - when additional Linux systems (typically z/VM guests) are added. This is
illustrated in Figure 3-7.
Consolidation of real distributed servers onto a zSeries platform, and in particular as guests
under z/VM (as illustrated in Figure 3-6 on page 30), can offer many advantages. Virtual
servers on z/VM share total system resources, such as memory and processor capacity, thus
optimizing resource utilization. Disk space can be also be shared amongst z/VM guests, and
in particular read-only files (like application code and operating systems software) can be
placed on one disk and made accessible to all the virtual Linux servers, thus minimizing
maintenance workload and software costs. z/VM also provides virtual networking and built-in
systems management functions, as described in 3.2, “Background to z/VM” on page 27.
Lightly to moderately loaded servers that do not peak concurrently are good candidates for
consolidating on a zSeries server running Linux.