Maximum number of supported paths reached

Products

• VMware vCenter Server
• VMware vSphere ESXi

Issue/Introduction

Symptoms

• The ESXi host system fails to report a physical path to storage.
• The maximum number of supported paths 1024 has been reached.
• If an ESXi host does not detect all the paths to the SAN, more than 1024 physical paths might be connected.
• You see this messages similar to:
  
  The maximum number of supported paths of 1024 has been reached. Path vmhba2:C0:T0:L3 could not be added. The number of paths allocated has reached the maximum: 1024. Path: vmhba5:C0:T6:L28 will not be allocated. This warning won't be repeated until some paths are removed.
   
• In the /var/log/vmkernel.log file of the ESXi host, you see entries similar to:
   
  WARNING: Number of devices allocated has reached the maximum: 1024. Device will not be allocated.

Impact

Storage paths that are discovered after the first 1024 are not added to the system. You will not have access to some of the storage paths, and possibly some storage devices, that are configured to be accessible by the system.

Environment

VMware vSphere ESXi 5.5
VMware vSphere ESXi 7.0.0
VMware vCenter Server 4.1.x
VMware vSphere ESXi 5.1
VMware vSphere ESXi 6.0
VMware vCenter Server 6.0.x
VMware vSphere ESXi 6.7
VMware vSphere ESXi 6.5

Resolution

To resolve this issue, reconfigure the storage attached to the ESXi host so that the total number of physical paths to storage is limited to 1024. For more information, see VMware Configuration Maximums.

To add more LUNs

1. Examine the LUNs the host has access to and identify the LUNs that it is not required to see.
2. Unpresent these LUNs.
3. Unmask the LUNs from ESX/ESXi before unpresenting them. For more information, see Masking a LUN from ESX and ESXi using the MASK_PATH plug-in (1009449).
4. Identify whether data on certain LUNs can be consolidated on to one LUN. Ensure that you use Storage vMotion or cold migration to move the data off a LUN if you are planning to consolidate data on to one LUN. You can then unpresent the LUNs from the host whose data has been consolidated.
5. Verify that the number of paths you have per LUN and whether you can reduce the number of paths, making sure that you do not compromise on both the HBA and the switch and controller.

Also, run this command on the ESXi host as root to view the number of LUNs seen by the VMkernel:

esxcli storage core device list |grep -E "^naa|^eui|^mpx|^t10" |wc -l