Book excerpt from VMware ESX and ESXi in the Enterprise

Chapter 6: Effects on Operations

The introduction of virtualization using VMware ESX and ESXi creates a myriad of operational problems for administrators, specifically problems having to do with the scheduling of various operations around the use of normal tools and other everyday activities, such as deployments, antivirus and other agent and agentless operational tasks (performance gathering, and so forth), virtual machine agility (vMotion and Storage vMotion), and backups. In the past, prior to quad-core CPUs, many of these limitations were based on CPU utilization, but now the limitations are in the areas of disk and network throughput.

The performance-gathering issues dictate which tools to use to gather performance data and how to use the tools that gather this data. A certain level of understanding is required to interpret the results, and this knowledge will assist in balancing the VMs across multiple ESX or ESXi hosts.

	Excerpt from VMware ESX and ESXi in the Enterprise: Planning Deployment of Virtualization Servers, 2nd Edition.
By Edward Haletky Published by Prentice Hall ISBN-10: 0-13-705897-7 ISBN-13: 978-0-13-705897-6

Newsletters: Sign-Up & Save! Receive Special Offers, Try Safari Books Online NOW.

The introduction of virtualization using VMware ESX and ESXi creates a myriad of operational problems for administrators, specifically problems having to do with the scheduling of various operations around the use of normal tools and other everyday activities, such as deployments, antivirus and other agent and agentless operational tasks (performance gathering, and so forth), virtual machine agility (vMotion and Storage vMotion), and backups. In the past, prior to quad-core CPUs, many of these limitations were based on CPU utilization, but now the limitations are in the areas of disk and network throughput.

The performance-gathering issues dictate which tools to use to gather performance data and how to use the tools that gather this data. A certain level of understanding is required to interpret the results, and this knowledge will assist in balancing the VMs across multiple ESX or ESXi hosts.

The disk throughput issues are based on the limited pipe between the virtualization host and the remote storage, as well as reservation or locking issues. Locking issues dictate quite a bit how ESX should be managed. As discussed in Chapter 5, “Storage with ESX,” SCSI reservations occur whenever the metadata of the VMFS is changed and the reservation happens for the whole LUN and not just an extent of the VMFS. This also dictates the layout of VMFS on each LUN; specifically, a VMFS should take up a whole LUN and not a part of the LUN. Disk throughput is becoming much more of an issue and will continue to be. Which is why with vSphere 4.1, Storage IO Control (SIOC) was introduced to traffic shape egress from the ESX host to Fibre Channel arrays. SIOC comes into play if the LUN latency is greater than 20ms. SIOC should improve overall throughput for those VMs marked as needing more of the limited pipe between the host and remote storage.

The network throughput issues are based on the limited pipes between the virtual machines and the outside physical network. Because these pipes are shared among many VMs, and most likely networks, via the use of VLANs, network I/O issues come to the forefront. This is especially true when discussing operational issues such as when to run network intensive tasks: VM backups, antivirus scans, and queries against other agents within VMs.

Virtual machine agility has its own operational and security concerns. Basically, the question is, “Can you ever be sure where your data is at any time?” Outside of the traditional operational concerns, virtual machine agility adds complexity to your environment.

Note that some of the solutions discussed within this chapter are utopian and not easy to implement within large-scale ESX environments. These are documented for completeness and to provide information that will aid in debugging these common problems. In addition, in this chapter unless otherwise mentioned we use the term ESX to also imply ESXi.