LUN filtering mechanism during RDM creation

Products

• VMware vCenter Server
• VMware vSphere ESXi

Issue/Introduction

When you create a virtual machine with an RDM, vCenter Server by default excludes LUNs that are already used for VMFS datastores or RDMs from the list of candidate target LUNs. Only unformatted LUNs are displayed for your selection.

This LUN filtering mechanism helps prevent LUN corruption that might occur if these conditions are not met:

• The same LUN cannot be used for a VMFS datastore and RDM simultaneously.
• Two virtual machines cannot have access to the same LUN using two different RDM mapping files.

Environment

VMware vCenter Server 7.x
VMware vCenter Server 6.x
VMware vSphere ESXi 6.x
VMware vSphere ESXi 7.x

Resolution

If you need virtual machines to access the same raw LUN, they must share the same RDM mapping file. For more information on this type of configuration, see Setup for Failover Clustering and Microsoft Cluster Service for ESXi 6.5

The config.vpxd.filter.rdmFilter and config.vpxd.filter.vmfsFilter configuration options in the vSphere Client control the LUN filtering mechanism. The options are set to true by default, but can be individually set to false when you need to turn off any of the filters.

However, you should not turn the filters off unless you have other methods to prevent LUN corruption.

Note: If you are upgrading your environment, check the values after the upgrade as the values can return to their default setting.

To turn off any of the filters using the vSphere Client:

1. In the vSphere Client, click Administration > vCenter Server Settings > Advanced Settings.
2. Depending on your needs, add one or both of these key and value pairs:
   
   
   • config.vpxd.filter.rdmFilter; false
   • config.vpxd.filter.vmfsFilter; false
     
     
3. Click Add, then click OK.
4. Highlight the affected ESXi host cluster and click on Rescan for Datastores.

Now, if you create a virtual machine with RDMs, all shared LUNs are displayed as RDM candidates even though they are already being used on a different ESXi/ESX host.

To turn on the filters again, set the values to true.

Note: For more information, refer to this KB article - Cannot see some or all storage devices in VMware vCenter Server or VirtualCenter (1016222)