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Slow performance on all virtual machines on an ESX host


You notice a slow performance on all virtual machines on an ESX host, too much IOWAIT?
Open a SSH session on your ESX host and run TOP, and check the IOWAIT% value. Is it constantly high?

Maybe your console is paging a lot!  Check the Swap used space, higher than 0K then it’s time to increase the memory allocated to your console.

To change the amount of RAM assigned to the service console:

  1. Log in to VirtualCenter from the Virtual Infrastructure Client with a user that has administrative rights.Note: If you do not have VirtualCenter, log in directly to the ESX Server host as root .
  2. From the Inventory select the ESX Server host.
  3. Click the Configuration tab.
  4. Click Memory.
  5. Click Properties.
  6. On the Memory window enter a value between 256MB and 800MB for the service console parameter.Note: For troubleshooting purposes, VMware recommends that you increase the service console RAM to 800MB.
  7. Click OK.

Reboot your ESX host and check again IOWAIT Swap used values…

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