When you set a limit on multiple virtual disks for a virtual machine is that all of these limits will be added up and that will be your threshold. In other words:

  • Disk01 – 50 IOps limit
  • Disk02 – 200 IOps limit
  • Combined total: 250 IOps limit
  • If Disk01 only uses 5 IOps then Disk02 can use 245 IOps!

There is one caveat though, “combined total” only goes for the disks which are stored on the same datastore. So if you have 4 disks and they are stored across 4 datastores then each of the individual limits apply respectively.


More details can be found in this KB article: http://kb.vmware.com/kb/1038241


By default, SIOC logging is disabled, but it should be enabled before collecting logs. To enable logging:

  1. Click Host Advanced Settings.
  2. In the Misc section, select the Misc.SIOControlLogLevel parameter. Set the value to 7 for complete logging.  (Min value: 0 (no logging), Max value: 7)
  3. SIOC needs to be restarted to change the log level, to stop and start SIOC manually, use:/etc/init.d/storageRM {start|stop|status|restart}
  4. After changing the log level, you see the log level changes logged in /var/log/vmkernel

Please note that SIOC log files are saved in /var/log/vmkernel.

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