ESX issues a SCSI_Inquiry, from VMware KB 1010244:

During a re-enumeration of storage devices, the VMware ESX/ESXi VMkernel sends SCSI Report LUNs command (0xa0) to the target to retrieve a list of LUNs, and SCSI Inquiry commands (0x12) to each LUN to determine the type of device (disk, CD-ROM, USB, etc), the make and model of the device, and the features the device supports.

A SCSI Inquiry requests Vital Product Data (VPD) page information from the LUN, including the unit serial number (page 0x80), a device identification number (page 0x83), and the management network address (page 0x85).

If a SCSI device does not support a particular VPD page, it may respond to such a request with an error. Specifically, it may return SCSI Status 2 (Check Condition), with sense key 5 (Illegal Request) and additional sense code (ASC) and additional sense code qualifier (ASCQ) set to 0x20/0x0 or 0x24/0x0.

Usually Local devices device don’t have page 83 information, but they do contain page 80 information. From the same KB:

Local storage devices often do not support VPD page 0x83, and thus cannot be used for Raw Device Mappings (RDMs). The content of page 0x83 is used as a unique identifier for the device.

CD or DVD-ROM devices often do not support VPD pages 0x80, 0x83 or 0x85. This can be ignored.

Some device controllers do not support Report LUNs. If there is no LUN 0, or the SCSI version reported is 2 or lower, the ESX/ESXi host iteratively scans for LUNs on this controller.

If you are using ESX classic then you can query both pages from your devices, here is an example:

[root@esx40u1 ~]# sg_vpd -p 0x83 /dev/sdd
Device Identification VPD page:
  Addressed logical unit:
    designator type: NAA, code_set: Binary
    Target port:
       designator type: vendor specific [0x0], code_set: ASCII
       transport: Internet SCSI (iSCSI)
          00 69 71 6e 2e 32 30 31 30 2d 30 39 2e 6f 72 67 2e 10 6f 70 65 6e 69 6e 64 69 61 6e 61 3a 30 32 3a 64
         openindiana:02:d 20 35 37 37 33 66 32 66 2d 64 35 62 31 2d 36 63 36 5773f2f-d5b1-6c6 30 31 2d 38 61 64 34 2d 62 35 61 32 64 61 63 33 34 1-8ad4-b5a2dac34 40 32 39 34 294
       designator type: Target port group, code_set: Binary
    Target port group: 0x0
       designator type: Relative target port, code_set: Binary
       Relative target port: 0x1

From the above output you can see the NAA ID of my OpenIndiana LUN presented over iSCSI. Here is an example of a device with both (it was a local drive):

[root@localhost ~]# sg_vpd -p 0x83 /dev/sda
Device Identification VPD page:
  Addressed logical unit:
   designator type: NAA, code_set: Binary

[root@localhost ~]# sg_vpd -p 0x80 /dev/sda
Unit serial number VPD page:
  Unit serial number: 6000c29e28495d0b9ecd280a8dc01a5c

You can see that the device has a Unit Serial Number and an NAA ID.

Published by Karim Elatov

18 August 2012