Datasheet

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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 NFSis 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 con 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, con 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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