Introduction to the HP Virtual Server Environment

Chapter 3: Virtualization Helps Reduce Overprovisioning
Virtualization can help reduce overprovisioning in many ways. It is no longer necessary to size a
server (or workload) for peak capacity or for unexpected future growth. The size of the various types
of partitions can be flexed with HP Instant Capacity (iCAP) or Temporary Instant Capacity (TiCAP)
processors. These processors can be dynamically reallocated between Virtual Partitions or even
shared with Integrity Virtual Machines (Integrity VM) or Secure Resource Partitions. New partitions
can be added or existing ones permanently resized (if necessary) much more quickly than bringing a
new server on line. The following sections describe these features in more detail.
Workloads Can Share Resources
The flexibility of virtualized environments means that resources that are not needed by one workload,
can be used by others. The graph in Figure 1 shows that the length of time that this workload needs
6 CPUs is very short, and that most of the time, the peak sustained load can be handled by 3 CPUs.
The other 3 CPUs can be put into a shared pool and can be used by whatever workload is peaking.
Even with this model, spare capacity is still needed. However, the amount of spare capacity required
is much lower because it can be shared by multiple workloads. Engineers in HP analyzed workloads
running on over 1300 servers and found that they were able to satisfy the peak loads of all
workloads in a consolidated environment using 40% fewer CPUs. For example, if 10 workloads
shared resources, as few as 36 CPUs, rather than 60, might satisfy their requirements.
Utility Resources Can Address Peaks
Many customers are uncomfortable running their environments without sufficient (guaranteed) spare
resources. To address this issue, HP offers Utility Pricing Solutions that can provide for the additional
capacity. In this way, in the unlikely case that several workloads become busy at the same time; the
customer can activate additional capacity if idle capacity on the system is insufficient. The following
paragraphs provide a brief overview of these HP solutions. Later sections discuss specific, related HP
technologies.
The iCAP solution allows customers to purchase a server with more CPUs than they need. The iCAP
CPUs are physically installed in the box but do not have usage rights; therefore, they are inactive and
are not used by the OS running on the system. At a later date, they can be activated with full usage
rights, and the bulk of the CPU cost is paid at activation time rather than at acquisition time. The
TiCAP solution allows activation of the iCAP CPUs (without full usage rights) for short periods of time
to handle peak loads.
Referring to the earlier 10-workload example, a customer can purchase a server with 64 CPUs in
order to consolidate the 10 workloads, but 36 of those CPUs can be permanent capacity and the
other 28 can be iCAP. This configuration costs much less than if all 64 CPUs were purchased
permanently. If you add to this some TiCAP licenses, you now have the ability to activate as many as
64 CPUs if all the workloads are busy at the same time. Although the situation where all workloads
peak at the same time is unlikely, it does provide a measure of safety that ensures that any
combination of spikes can be handled by the server. In addition, the cost is reduced because the
customer pays for only the CPUs that are actually turned on.
Flexibility Simplifies Capacity Planning
The flexibility inherent in these HP solutions drastically reduces the risk of underprovisioning. If one of
the workloads turns out to be larger than expected, or if it grows faster than expected, the system has
enough spare resources to satisfy the application almost instantly. You no longer need to purchase a
larger server and migrate the workload; you simply activate some additional resources and assign
them to the workload.
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