Newly added LUNs are not visible on an ESXi/ESX host

Products

• VMware vSphere ESXi

Issue/Introduction

Symptoms:

• Newly presented LUNs do not appear in the GUI
• This issue occurs when you present LUNs from the same or a new storage array
• LUNs are not detected on the host even after multiple rescan attempts

Environment

VMware ESXi 4.0.x Embedded
VMware ESXi 4.0.x Installable
VMware ESX 4.0.x
VMware vSphere ESXi 5.0
VMware ESXi 3.5.x Embedded
VMware ESXi 3.5.x Installable
VMware ESX 4.1.x
VMware vSphere ESXi 5.1
VMware ESXi 4.1.x Embedded
VMware ESXi 4.1.x Installable
VMware ESX Server 3.5.x

Cause

There is a limit on the number of LUNs accessible to an ESXi/ESX host. For ESXi/ESX 3.x and later, this limit is 256 LUNs. When the number of LUNs presented to the host exceeds this value, some LUNs will not be visible to the host.

Note: There is also a limit to the number of paths an ESXi/ESX host can have to storage LUNs. It is possible that the host may have a large number of paths per LUN that could also prevent the discovery of additional LUNs before the limit in quantity of LUNs is reached. For ESXi/ESX 3.x and later, this limit is 1024 paths per ESXi/ESX host.

For a more complete listing on storage limitations, see ESXi/ESX Configuration Maximums (1003497).

Resolution

To resolve this issue, you must reduce the total number of LUNs or paths to LUNs in the environment to remain within supported limitations as defined in the vSphere Configuration Maximums guide.

This can be accomplished by masking unneeded LUNs at the storage array to ensure only required LUNs are visible to each ESXi/ESX host, or by modifying the storage network zoning in a fibre channel network. For more information, contact your storage vendor to discuss these options.

Additional Information

ESXi/ESX Configuration Maximums
Understanding storage device detection in ESXi