By default, Dynamic Multi-Pathing (DMP) assigns enclosure-based names to DMP metadevices using an array-specific attribute called the Array Volume ID (AVID). The AVID provides a unique identifier for the LUN that is provided by the array. The ASL corresponding to the array provides the AVID property. Within an array enclosure, DMP uses the Array Volume Identifier (AVID) as an index in the DMP metanode name. The DMP metanode name is in the format enclosureID_AVID.
With the introduction of AVID to the enclosure-based naming (EBN) naming scheme, identifying storage devices becomes much easier. The array volume identifier (AVID) enables you to have consistent device naming across multiple nodes connected to the same storage. The disk access name never changes, because it is based on the name defined by the array itself.
If DMP does not have access to a device's AVID, it retrieves another unique LUN identifier called the LUN serial number. DMP sorts the devices based on the LUN Serial Number (LSN), and then assigns the index number. All hosts see the same set of devices, so all hosts will have the same sorted list, leading to consistent device indices across the cluster. In this case, the DMP metanode name is in the format enclosureID_index.
DMP also supports a scalable framework, that allows you to fully customize the device names on a host by applying a device naming file that associates custom names with cabinet and LUN serial numbers.
If a Cluster Volume Manager (CVM) cluster is symmetric, each node in the cluster accesses the same set of disks. Enclosure-based names provide a consistent naming system so that the device names are the same on each node.
The Dynamic Multi-Pathing (DMP) utilities such as vxdisk list display the DMP metanode name, which includes the AVID property. Use the AVID to correlate the DMP metanode name to the LUN displayed in the array management interface (GUI or CLI) .
For example, on an EMC CX array where the enclosure is emc_clariion0 and the array volume ID provided by the ASL is 91, the DMP metanode name is emc_clariion0_91. The following sample output shows the DMP metanode names:
$ vxdisk list emc_clariion0_91 auto:cdsdisk emc_clariion0_91 dg1 online shared emc_clariion0_92 auto:cdsdisk emc_clariion0_92 dg1 online shared emc_clariion0_93 auto:cdsdisk emc_clariion0_93 dg1 online shared emc_clariion0_282 auto:cdsdisk emc_clariion0_282 dg1 online shared emc_clariion0_283 auto:cdsdisk emc_clariion0_283 dg1 online shared emc_clariion0_284 auto:cdsdisk emc_clariion0_284 dg1 online shared
# vxddladm get namingscheme NAMING_SCHEME PERSISTENCE LOWERCASE USE_AVID ========================================================== Enclosure Based Yes Yes Yes