Storage Device Names and Identifiers

In the ESXi environment, each storage device is identified by several names.

Device Identifiers

Depending on the type of storage, the ESXi host uses different algorithms and conventions to generate an identifier for each storage device.

Storage-provided identifiers

The ESXi host queries a target storage device for the device name. From the returned metadata, the host extracts or generates a unique identifier for the device. The identifier is based on specific storage standards, is unique and persistent across all hosts, and has one of the following formats:

• naa.xxx
• eui.xxx
• t10.xxx

Path-based identifier

When the device does not provide an identifier, the host generates an mpx. path name, where path represents the first path to the device, for example, mpx.vmhba1:C0:T1:L3. This identifier can be used in the same way as the storage-provided identifies.

The mpx.path identifier is created for local devices on the assumption that their path names are unique. However, this identifier is not unique or persistent, and can change after every system restart.

Typically, the path to the device has the following format:

vmhbaAdapter:CChannel:TTarget:LLUN

• vmhbaAdapter is the name of the storage adapter. The name refers to the physical adapter on the host, not to the SCSI controller used by the virtual machines.
• CChannel is the storage channel number.

  Software iSCSI adapters and dependent hardware adapters use the channel number to show multiple paths to the same target.

• TTarget is the target number. Target numbering is determined by the host and might change when the mappings of targets visible to the host change. Targets that are shared by different hosts might not have the same target number.
• LLUN is the LUN number that shows the position of the LUN within the target. The LUN number is provided by the storage system. If a target has only one LUN, the LUN number is always zero (0).

For example, vmhba1:C0:T3:L1 represents LUN1 on target 3 accessed through the storage adapter vmhba1 and channel 0.

Legacy identifier

In addition to the device-provided identifiers or mpx. path identifiers, ESXi generates an alternative legacy name for each device. The identifier has the following format:

vml.number

The legacy identifier includes a series of digits that are unique to the device. The identifier can be derived in part from the metadata obtained through the SCSI INQUIRY command. For nonlocal devices that do not provide SCSI INQUIRY identifiers, the vml.number identifier is used as the only available unique identifier.

Displaying Device Names in the vSphere CLI

You can use the esxcli storage core device list command to display all device names in the vSphere CLI. The output is similar to the following example:

# esxcli storage core device list
naa.XXX
	  Display Name: DGC Fibre Channel Disk(naa.XXX)
	  ... 
	  Other UIDs: vml.000XXX
mpx.vmhba1:C0:T0:L0
   Display Name: Local VMware Disk (mpx.vmhba1:C0:T0:L0)
   ...
   Other UIDs: vml.0000000000XYZ