Information Technology Reference
In-Depth Information
no overhead, which we've already shown you isn't the case) and will run in real RAM. If an
administrator tried to run 20 VMs coni gured for 2,048 MB of RAM, then all 20 VMs will share
the 24,576 MB of RAM, even though their requirement is for 40,960 MB (20 × 2,048 MB)—the
remaining amount of RAM would most likely be provided by VMkernel swap. At this point,
performance would be noticeably slow.
If you want to clear a limit, select Unlimited from the Limit drop-down menu. This is true
for both CPU limits as well as memory limits. By now you should have a fair idea of how ESXi
allocates resources to VMs as well as how you can tweak those settings to meet your specii c
demands and workloads.
As you can see, if you have groups of VMs with similar resource demands, using resource
pools is an excellent way of ensuring consistent resource allocation. As long as you understand
the hierarchical nature of resource pools—that resources are allocated i rst to the pool at its level
in the hierarchy, and then the VMs in the pool—then you should be able to use resource pools
effectively.
So far you've seen how to control the use of CPU and memory, but those are only two of the
four major resources consumed by VMs. In the next section, you'll see how to control network
trafi c through network resource pools.
Regulating Network I/O Utilization
The resource pools we've shown you so far can only be used to control CPU and memory usage.
However, vSphere offers another type of resource pool, a
network
resource
pool
that allows you to
control network utilization. Using network resource pools—to which are assigned shares and
limits—you can control incoming and outgoing network trafi c. This feature is referred to as
vSphere Network I/O Control (NIOC).
Only on a Distributed Switch
vSphere Network I/O Control applies only to vSphere Distributed Switches (vDS) version 4.1.0 or
later and, prior to version 5.1.0, is limited to outbound network tra c only. Refer to Chapter 5,
“Creating and Confi guring Virtual Networks,” for more information on setting up or confi guring
a vDS.
When you enable vSphere NIOC, vSphere activates eight predei ned network resource pools:
NFS Trafi c
◆
Management Trafi c
◆
vMotion Trafi c
◆
vSphere Storage Area Network Trafi c
◆
vSphere Replication (VR) Trafi c
◆
iSCSI Trafi c
◆
Virtual Machine Trafi c
◆
Fault Tolerance (FT) Trafi c
◆
