Monday, November 14, 2011

VCP5 - Enable/Configure/Disable hyperthreading

Hyperthreading has historically been a troublesome issue. The precursor to multiple cores, the idea is to run multiple commands through the same processor at the same time - thereby simulating multiple cores. This worked well with some applications, but caused nightmares for others. The good news is that Hyperthreading has been rebuilt with the latest generation of processors, and specifically tuned for VMware.

To enable/disable Hyperthreading in ESXi

  1. Configure the system BIOS to enable/disable hyperthreading
  2. Open Virtual Center and select Hosts and Clusters
  3. Select the host and click the Configuration tab
  4. Select Hardware | Processors - here you can view the current Hyperthreading settings
  5. Click Properties to change the Hyperthreading

Once enabled, Hyperthreading is defaulted to be used by all VMs in a fashion similar to multi-core processors. This sharing can be configured on a per-VM basis and be set to ANY (default), NONE (no hyperthreading), and Internal (hyperthreading only with itself). These configurations exist to stabilize individual VMs, but should be used with care.
Configuring Hyperthreading in ESXi
  1. Open Virtual Center and select VMs and Templates
  2. Select the VM and click Edit Settings
  3. On the Resources tab, select Advanced CPU to change the settings

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