2010-11-12

Performande Best Practices for VMware vSphere 4.1

Nytt white paper från VMware: Performance Best Practices for VMware vSphere 4.1
Ett fullmatat dokument på 60 sidor med massor med bra tips.
Huvudrubriker:
- Hardware for user with VMware vSphere
- ESX and Virtual Machines
- Guest Operating systems
- Virtual Infrastrucure Management

Några saker jag speciellt gillar:

It is a good idea to periodically monitor the CPU usage of the host. This can be done through the vSphere Client or by using esxtop or resextop. Below we describe how to interpret esxtop data:
• If the load average on the first line of the esxtop CPU panel is equal to the number of physical processors in the system, this indicates that the system is overloaded.
• The usage percentage for the physical CPUs on the PCPU line can be another indication of a possibly overloaded condition. In general, 80% usage is a reasonable ceiling and 90% should be a warning that the CPUs are approaching an overloaded condition. However organizations will have varying standards regarding the desired load percentage.
For information about using esxtop or resextop see Appendix A of the VMware Resource Management Guide.
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Most guest operating systems execute an idle loop during periods of inactivity. Within this loop, most of these guest operating systems halt by executing the HLT or MWAIT instructions. Some older guest operating systems, however, use busy-waiting within their idle loops. This results in the consumption of resources that might otherwise be available for other uses (other virtual machines, the VMkernel, the console, etc.). (These older operating systems include Windows 2000 (with certain HALs), Solaris 8 and 9, and MS-DOS.) For additional information see VMware KB articles 1077 and 2231. (http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1077)

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UP vs. SMP HALs/Kernels
• Although some recent operating systems (including Windows Vista, Windows Server 2008, and Windows 7) use the same HAL (hardware abstraction layer) or kernel for both UP and SMP installations, many operating systems can be configured to use either a UP HAL/kernel or an SMP HAL/kernel. To obtain the best performance on a single-vCPU virtual machine running an operating system that offers both UP and SMP HALs/kernels, configure the operating system with a UP HAL or kernel.
The UP operating system versions are for single-processor systems. If used on a multiprocessor system, a UP operating system version will recognize and use only one of the processors. The SMP versions, while required in order to fully utilize multiprocessor systems, may also be used on single-processor systems. Due to their extra synchronization code, however, SMP operating system versions used on single-processor systems are slightly slower than UP operating system versions used on the same systems.

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Memory Overcommit Techniques
While ESX uses page sharing and ballooning to allow significant memory overcommitment, usually with  little or no impact on performance, you should avoid overcommitting memory to the point that it requires host-level swapping.
If you suspect that memory overcommitment is beginning to affect the performance of a virtual machine you can:
• Look at the value of Memory Balloon (Average) in the vSphere Client Performance Chart. An absence of ballooning suggests that ESX is not under heavy memory pressure and thus memory overcommitment is not affecting performance. (Note, however, that some ballooning is quite normal and not indicative of a problem.)
• Check for guest swap activity within that virtual machine. This can indicate that ballooning might be starting to impact performance, though swap activity can also be related to other issues entirely within the guest (or can be an indication that the guest memory size is simply too small).
• Look at the value of Memory Swap Used (Average) in the vSphere Client Performance Chart. Memory swapping at the host level would indicate more significant memory pressure



Det skall sägas att många av de tips som står i detta dokument även funkar på andra virtualiseringsplattformar (ex. XenServer, Hyper-V).


Men inte bara det. Mycket är även relevant för vanliga Windowsburkar....
Jag har tidigare tagit upp tre riktigt bra dokument kring detta:
Windows 2003: http://download.microsoft.com/download/2/8/0/2800a518-7ac6-4aac-bd85-74d2c52e1ec6/tuning.doc

Windows 2008: http://www.microsoft.com/whdc/system/sysperf/Perf_tun_srv.mspx
Windows 2008 R2: http://www.microsoft.com/whdc/system/sysperf/Perf_tun_srv-R2.mspx

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