Information Technology Reference
In-Depth Information
Chapter 12
Balancing Resource Utilization
Virtualization with VMware vSphere is, among other things, about getting better utilization of
your computing resources within a single physical host. vSphere accomplishes this by letting
you run multiple instances of a guest operating system on a single physical host. However, it's
also about getting better resource utilization across multiple physical hosts, and that means
shifting workloads between hosts to balance the resource utilization. vSphere offers a number
of powerful tools for helping administrators balance resource utilization.
In this chapter, you will learn to
Coni gure and execute vMotion
◆
Ensure vMotion compatibility across processor families
◆
◆
Use Storage vMotion
Perform Combined vMotion and Storage vMotion
◆
Coni gure and manage vSphere Distributed Resource Scheduler
◆
Coni gure and manage Storage DRS
◆
Comparing Utilization with Allocation
The fundamental but subtle difference between allocation and utilization can be difi cult to
understand at times.
Allocation
is about how a resource is assigned; so in a vSphere environ-
ment, allocation is about how CPU cycles, memory, storage I/O, and network bandwidth are
distributed to a particular VM or group of VMs.
Utilization
, on the other hand, is about how
resources are used after they are allocated. vSphere provides three mechanisms for allocation:
reservations (guaranteed allocations of resources), limits (bounds on the maximum allocation
of resources), and shares (prioritized access to resource allocation during periods of resource
contention). While these mechanisms are powerful and useful—as you saw in Chapter 11,
“Managing Resource Allocation”—they do have their limits (no pun intended). What about situ-
ations when a resource is highly utilized on one host and lightly utilized on another host? None
of the three mechanisms we've shown you so far will help balance the
utilization
of resources
among ESXi hosts; they will only control the
allocation
of resources.
VMware vSphere helps balance the intra-cluster utilization of resources in the following
four ways:
vMotion
vMotion, also generically known as
live
migration
, is used to manually balance
compute resource utilization between two ESXi hosts.
