7.8.23 Tracing a volume from a host back to its physical disks In some cases, you might need to verify exactly which physical disks are used to store data of  a volume. This information is not directly available to the host; however, it might be obtained  by using a sequence of queries.  The first step is to unequivocally map a logical device seen by the host to a volume that is  presented by the storage system. The best volume characteristics for this purpose is the  volume ID. This ID is available to the operating system in the Vendor Specified Identifier field  of page 0x80 or 0x83 (vital product data, VPD), which the storage device sends in response  to SCSI INQUIRY command from the host.  In practice, the ID can be obtained from the multipath driver in the operating system. After the  volume ID is known, it can be used to identify physical location of data.  Note:  For sequential and image mode volumes, a volume copy is mapped to exactly one  MDisk. This configuration often is not the case for stripped volumes, unless volume size is  not greater than an extent size. Therefore, a single stripped volume uses multiple mDisks  in a typical case. On hosts that are running IBM System Storage Multipath Subsystem Device Driver, you can  obtain the volume ID from the output of the  datapath query device  command. You see a long  disk serial number for each vpath device, as shown in Example 7-37. State:  In Example 7-38, the state of each path is  OPEN . Sometimes, the state is  CLOSED .  This state does not necessarily indicate a problem because it might be a result of the  path’s processing stage.  DEV#: 0 DEVICE NAME: Disk1 Part0 TYPE: 2145 POLICY: OPTIMIZED SERIAL: 60050768018301BF2800000000000005 ============================================================================ Path# Adapter/Hard Disk State Mode Select Errors 0 Scsi Port2 Bus0/Disk1 Part0 OPEN NORMAL 20 0 1 Scsi Port3 Bus0/Disk1 Part0 OPEN NORMAL 2343 0 DEV#: 1 DEVICE NAME: Disk2 Part0 TYPE: 2145 POLICY: OPTIMIZED SERIAL: 60050768018301BF2800000000000004 ============================================================================ Path# Adapter/Hard Disk State Mode Select Errors 0 Scsi Port2 Bus0/Disk2 Part0 OPEN NORMAL 2335 0 1 Scsi Port3 Bus0/Disk2 Part0 OPEN NORMAL 0 0 DEV#: 2 DEVICE NAME: Disk3 Part0 TYPE: 2145 POLICY: OPTIMIZED SERIAL: 60050768018301BF2800000000000006 ============================================================================ Path# Adapter/Hard Disk State Mode Select Errors 0 Scsi Port2 Bus0/Disk3 Part0 OPEN NORMAL 2331 0 1 Scsi Port3 Bus0/Disk3 Part0 OPEN NORMAL 0 0 Example 7-37 The datapath query device command 314  Implementing the IBM Storwize V7000 with IBM Spectrum Virtualize V8.2.1