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6: A Most-Significant Step—“Virtualizing” Your IT Systems 99

Cloud Computing—The Exciting Future

Cloud computing is a new (circa late 2007) label for the subset of grid
computing that includes utility computing and other approaches to the use
of shared computing resources. Cloud computing is an alternative to having
local servers or personal devices handling users’ applications. Essentially, it is
an idea that the technological capabilities should “hover” over everything
and be available whenever a user wants. See Appendix B for details.

Cluster Architecture for Virtual Servers

As discussed previously in this chapter, there are now many IT vendors
with virtual servers and other virtual systems. Also briefly discussed was
VMware’s technology for moving servers called VMotion. By completely vir-
tualizing servers, storage, and networking, an entire running virtual machine
can be moved instantaneously from one server to another. I’ve worked with
VMotion implementations on projects at data centers, and it does seem to be
a step in the direction in support of the grid and cloud computing concepts
ptg
discussed in this chapter.

VMware Clusters (VMotion)
The entire state of a virtual machine is encapsulated by a set of files stored
on shared storage, and VMware’s VMFS cluster file system allows both the
source and the target VMware ESX server to access these virtual machine files
concurrently. The active memory and precise execution state of a virtual
machine can then be rapidly transmitted over a high-speed network. Because
the network is also virtualized by VMware ESX, the virtual machine retains
its network identity and connections, ensuring a seamless migration process.
VMotion servers require external shared storage (SAN).
Figures 6.5 and 6.6 show the VMotion concept and four node cluster
examples implemented at a large data center outside of Chicago. The concept
of using VMotion clusters for all VMware server needs has worked very well
and has basically eliminated the previous need to manage and balance the
load among difference physical servers used to host VMware virtual servers.
Figure 6.5 shows the general VMware cluster (VMotion) concept used at this
data center. Figure 6.6 shows one of the two clusters used.