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
them.
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
(consolidation).
3.3.1 Scalability
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.
3.3.2 Consolidation
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.
30 Linux with zSeries and ESS - Essentials
Figure 3-6 Server farm in a box
Some key applications are usually deployed in a three-tiered mode; a database tier, an
application tier, and a presentation tier. In a hybrid z/OS and Linux for zSeries environment,
the database server resides on a z/OS image, while the application server runs on a Linux for
zSeries instance. Both reside on the same hardware, enabling the customer to remove a
layer of hardware and maintenance effort while still meeting the performance requirements
that the solution demands. In addition, with the application and database now hosted on the
one system, the real networks between them can be replaced by the networking features of
zSeries (such as Hipersockets).
When servers have been consolidated onto a zSeries server, and in particular when running
as z/VM guests, the horizontal growth of your server farm can be accomplished with minimal
time (typically minutes), and without requiring additional hardware or real estate, by simply
adding another Linux virtual machine. This is shown in Figure 3-7. Moreover, you are still able
to maintain the distributed environment paradigm of “one server one application.
Figure 3-7 Horizontal server growth
A number of the features and benefits discussed above are illustrated in “Typical file/print
serving scenario with Samba” on page 31, where we outline a scenario in which multiple
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