Datasheet

Lowe c01.indd V3 - 08/11/2011 Page 10

CHAPTER 1 INTRODUCING VMWARE VSPHERE 5

vMotion Enhancements

vSphere 5 enhances vMotion’s functionality, making VM migrations faster and enabling more

concurrent VM migrations than were supported in previous versions of vSphere or VMware

Infrastructure 3. vSphere 5 also enhances vMotion to take advantage of multiple network inter-

faces, further improving live migration performance.

vMotion moves the execution of a VM, relocating the CPU and memory footprint between

physical servers but leaving the storage untouched. Storage vMotion builds on the idea and

principle of vMotion by providing the ability to leave the CPU and memory footprint untouched

on a physical server but migrating a VM’s storage while the VM is still running.

Deploying vSphere in your environment generally means that lots of shared storage—Fibre

Channel or iSCSI SAN or NFS—is needed. What happens when you need to migrate from an

older storage array to a newer storage array? What kind of downtime would be required? Or

what about a situation where you need to rebalance utilization of the array, either from a capac-

ity or performance perspective?

vSphere Storage vMotion directly addresses these situations. By providing the ability to move

the storage for a running VM between datastores, Storage vMotion enables administrators to

address all of these situations without downtime. This feature ensures that outgrowing datastores

or moving to a new SAN does not force an outage for the affected VMs and provides administra-

tors with yet another tool to increase their ﬂ exibility in responding to changing business needs.

VSPHERE DISTRIBUTED RESOURCE SCHEDULER

vMotion is a manual operation, meaning that an administrator must initiate the vMotion opera-

tion. What if VMware vSphere could perform vMotion operations automatically? That is the

basic idea behind vSphere Distributed Resource Scheduler (DRS). If you think that vMotion

sounds exciting, your anticipation will only grow after learning about DRS. DRS, simply put,

leverages vMotion to provide automatic distribution of resource utilization across multiple ESXi

hosts that are conﬁ gured in a cluster.

Given the prevalence of Microsoft Windows Server in today’s datacenters, the use of the

term cluster often draws IT professionals into thoughts of Microsoft Windows Server clusters.

Windows Server clusters are often active-passive or active-active-passive clusters. However,

ESXi clusters are fundamentally different, operating in an active-active mode to aggregate and

combine resources into a shared pool. Although the underlying concept of aggregating physical

hardware to serve a common goal is the same, the technology, conﬁ guration, and feature sets

are quite different between VMware ESXi clusters and Windows Server clusters.

Aggregate Capacity and Single Host Capacity

Although I say that a DRS cluster is an implicit aggregation of CPU and memory capacity, it’s impor-

tant to keep in mind that a VM is limited to using the CPU and RAM of a single physical host at any

given time. If you have two ESXi servers with 32 GB of RAM each in a DRS cluster, the cluster will

correctly report 64 GB of aggregate RAM available, but any given VM will not be able to use more

than approximately 32 GB of RAM at a time.

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