eWeek - July 19, 2010

capacity of VMware vSphere 4.0.

Aside from the sizable scale increase enabled in this version of vSphere 4.1, the main advances in the platform are evolutionary extensions of capabilities that improve how the platform handles VM resource contention. During tests, I used the new I/O controls in networking and storage to govern resource use.

IT managers who are already accustomed to using resource controls in VM CPU settings will have a leg up when it comes to using I/O controls in both network and storage areas. Even with the CPU control heritage, my use of network and storage control features revealed a fair number of “version 1” limitations.

Network I/O control prioritizes network traffic by type when using network resource pools and the native VMware vNetwork Distributed Switch. Network I/O control works only with the 4.1 version of the vNetwork Distributed Switch—not with the Cisco Nexus V1000 or the standard switch from VMware.

Implementation is simple

While it takes advanced network expertise to design and tune the policy that runs network I/O controls, the implementation of the feature is quite simple. Entering the parameter changes to enable the feature and set the specific physical network adapter shares is simply a matter of walking through a couple of configuration screens that are easily accessed from the vSphere client.

I was able to assign a low, medium,
normal, high or custom setting
that designated the number of net-
work shares (a policy designation
that represents the relative impor-
tance of virtual machines that are
using the same shared resources)
that would be allocated to virtual
machine, management and fault-
tolerant traffic flows.

Storage I/O controls were equally easy to configure once the policy decisions and physical prerequisites were met. In my relatively modest test environment, it was no trouble to run storage I/O controls on a single vCenter Server. I tested this feature on an iSCSI-connected storage array. It also works on Fibre Channel-con-nected storage, but not on NFS or Raw Device Mapping storage.

Virtual machines can be limited based on IOPS (I/O operations per second) or MB per second. In either case, I used storage I/O controls to limit some virtual machines in order to give others priority.

I found that the large number of considerations—for example, each virtual disk associated with each VM must be placed under control for the limit to be enforced—meant that I spent a great deal of time figuring policy to get a modest amount of benefit when my systems were running.

Memory innovation

VMware included a handy memory innovation in vSphere 4.1 called Since accessing this memory is significantly faster than swapping memory pages to disk, the virtual machines ran much faster with this feature than they did when it was disabled and the same workloads were started.

IT managers should expect to devote at least several weeks of expert analysis to determine the most effective memory compression configuration for each workload.

VMware did some housekeeping in the incremental release of vSphere. The vSphere client is still available in the vCenter 4.1 installation bits, but it is no longer included in the ESX and ESXi code. There also were some minor changes made to various interface screens, but there was nothing that would puzzle an experienced IT administrator. ;