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From: www.itworld.com
Book: VMware ESX Server in the Enterprise
August 27, 2008 —
VMware ESX Server in the Enterprise is the definitive, real-world guide to planning, deploying, and managing today’s leading virtual infrastructure platform in mission-critical environments. It covers the entire lifecycle: planning, installation, system monitoring, tuning, clustering, security, disaster recovery, and much more. The book also includes detailed checklists for handling crucial issues such as caching, networking, storage, and hardware selection. The chapter available for download here covers data store performance or bandwidth issues, SCSI-2 reservation issues, and performance-gathering agents.
From Chapter 6: Effects on Operations:
ESX creates a myriad of 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, VMotion to balance nodes, and backups. Most, if not all, the limitations revolve around issues related to performance gathering and the data stores upon which VMs are placed, whether SCSI, including iSCSI, or non-VMDK files accessed from NFS shared off a NAS or some other system.
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 Servers.
The data store limitations consist of bandwidth issues; each has a limited pipe between the ESX Server and the remote storage and reservation or locking issues. These two issues dictate quite a bit how ESX should be managed. As discussed in Chapter 5, “Storage with ESX,†SCSI reservations will occur whenever the metadata of the VMFS is changed and the reservation happens for the whole LUN and not an extent of the LUN. 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.
This chapter covers data store performance or bandwidth issues, SCSI-2 reservation issues, and performance-gathering agents, and then finishes with some other issues and a discussion of the impact of Sarbanes-Oxley. 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 give information that will aid in debugging these common problems.
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Prentice Hall