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Tuesday, 16 April 2013

How to disable automatic rescan of HBAs initiated by vCenter (1016873)


When you create, expand, extent, or delete a datastore, a rescan of your HBAs is automatically initiated. However, this rescan may result in a “rescan storm” when you are building a new environment and may result in issues such as, packet drops and poor performance. In such cases, you may want to disable auto-rescan.
This article provides the steps to disable auto-rescan.
Note: Auto-rescan enables other hosts in the cluster to recognize and use a newly created datastore immediately. Disabling auto-rescan may create issues when the hosts are unable to recognize datastores. For example, during vMotion, the destination host may reject the request because it is unable to recognize the datastore created by the source host. VMware recommends you to disable auto-rescan only when building a new environment.


To disable auto-rescan:
  1. Open the vSphere Client.
  2. Go to Administration > vCenter Server.
  3. Go to Settings > Advanced Settings.
  4. If the config.vpxd.filter.hostRescanFilter key is not available, add the key and set it to False.

     You need not restart vCenter Server for the change to take effect.
Note: If you turn off the Host Rescan Filter, your hosts continue to perform a rescan each time you present a new LUN to a host or a cluster. This can be seen in the Task & Events pane.

Additional Information

Ensure to set the config.vpxd.filter.hostRescanFilter key to True immediately after building your environment.
vCenter Server may display an error if you try to reset the value using the GUI. In such a case, you must manually edit the vpxd.cfg file to enable auto-rescan.
To enable auto-rescan by manually editing the vpxd.cfg file:
  1. Open the file using a text editor.
  2. Locate the <hostRescanFilter> entry.
  3. Set the entry to False:

  4. Restart the VMware VirtualCenter Server service.

For more/related information, see the Turn off vcenter server storage filters section of the ESX 4.1 Configuration Guide or ESXi 5.0 Storage Guide