Hardware Management - Deploying and Managing a Cloud Infrastructure - page 242

Another choice you have it what kind of storage media to use: tape, disk, or SSD. Tape
is the cheapest, with the most capacity but the worst performance. Hard disks are between
tape and SSDs when it comes to performance and capacity, while SSDs have less capacity
but offer the best performance.
With all of these resources at your disposal, if you are the host, you have to be able to
allocate them properly lest you have shortages and be unable to meet your service-level
agreements. You can allocate each virtual resource differently; you can even set up various
algorithms for proper allocation. The most visible of these measures are the different service
packages that we make available to our customers. Service packages also effectively allow us
to estimate the total tenant capacity of the infrastructure.
Conversely, if you are the customer, your view of proper resource allocation is no longer
on how you can extend your finite resources but how to effectively make do with what you
have and maintain peak performance while lowering costs. The best way to achieve this is
to have a lean approach, which is to allocate only enough resources for satisfactory perfor-
mance of virtual machines.
You learned in this chapter how different the management approach is for a public and
private cloud. Public clouds are managed with economies of scale and cost efficiency in
mind, while management of private clouds is geared more toward proper resource allocation
and authorization.
Finally, we covered the different tier levels for storage configuration, how each one is
used, and what technology is attached to each. We then explained how RAID levels differ
from each other and the nuances of each level.
Chapter Essentials
BIOS/Firmware Configuration BIOS configuration is a good way to improve virtual
machine performance by tweaking various settings that would be available in a physical
computer. The difference is that a VM has no proper BIOS that can be set up; this has to
be explicitly made available by the service provider.
Minimum Memory Capacity and Configuration Each VM instance should be allocated
the memory it requires, not less or more. The problem with allocating too much memory
is that not all of it will be utilized, removing it from the resource pool when it could have
been allocated to another VM. Memory also incurs more costs; multiply the memory by
the number of VMs, and it could become a staggering amount.
Number of CPUs The number of CPUs that can be allocated to a VM instance depends
on the service package in use. Lesser packages allow for only a single CPU for each VM,
which may not be enough for the type of workload necessary for that VM. In such cases,
a higher-level service package should be availed.
Number of Cores The number of cores that a host contains is doubled if hyperthreading
is enabled. This means that if a host has 4 physical CPUs with 4 cores each, totaling to 16
logical CPUs, it can support virtual machines, which can have up to 16 single-core vCPUs.