Problem

Explanation of what the udid_mismatch flag indicates in vxdisk list output

Solution

UDID stands for Unique Device Identification. This is a feature introduced beginning in Storage Foundation 5.0 that was designed to enable import of cloned LUNs presented on the same host as the source disks.

A UDID is generated for every device discovered by Volume Manager and is composed of the following information:

Vendor ID (VID) Product ID (PID) Cabinet Serial Number (Array serial number) LUN Serial Number (Serial number for LUN on array)

This string is visible in "vxdisk list (device)" output:

# vxdisk list ams_wms0_5 | grep udidudid: HITACHI%5FDF600F%5F73061247%5F0005

The component parts are separated by the '_' character, encoded here as %5F, so we can readily observe the following from the above string:VID = HITACHIPID = DF600FCabinet Serial Number = 73061247LUN Serial Number = 0005

It is important to note that Cabinet/LUN serial numbers are different than the SCSI serial number. SCSI serial numbers are encoded differently on a frame by frame basis. For instance, the AMS/WMS frames will present the SCSI serial number as a combination for Cabinet and LUN:

# /etc/vx/diag.d/vxdmpinq /dev/rdsk/c0t50060E80104EF3F0d1s2

Inquiry for /dev/rdsk/c0t50060E80104EF3F0d1s2, evpd 0x0, page code 0x0Vendor id : HITACHIProduct id : DF600FRevision : 0000Serial Number : 730612470005

(NOTE: In 5.1 the vxdmpinq command has been renamed vxscsiinq.)

What "udid_mismatch" indicates:

# vxdisk listDEVICE TYPE DISK GROUP STATUSams_wms0_4 auto:cdsdisk d01 nadg onlineams_wms0_5 auto:cdsdisk - - online udid_mismatchdisk_0 auto:none - - online invaliddisk_1 auto:none - - online invalid

In this example, the ams_wms0_5 device was created as an atomic bit-for-bit copy of the ams_wms0_4 LUN.

# /etc/vx/diag.d/vxprivutil list /dev/rdsk/c0t50060E80104EF3F0d1s2 | grep udidtagid priv 2016- 2031[ 16]: tag=udid_asl=HITACHI%5FDF600F%5F73061247%5F0004

Compare this UDID with the UDID above from ams_wms0_4. 

This device is being labeled as 'udid_mismatch' because the current device's UDID string does not match the UDID string stored in the disk's private region.

This is an expected condition for LUNs created through processes such as BCV, Shadow Copy, or any other LUN duplicate methods. The this is because the physical device's information is different than the original source LUNs.

In most environments this flag can be ignored as an expected result of presenting duplicated Volume Manager initialized LUNs.

For environments where this flag is undesired, the cloned disk groups can be imported with the following parameter to change the udid_mismatch flag into the 'cloned' flag:

# vxdg -o useclonedev=on import nadg# vxdisk listDEVICE TYPE DISK GROUP STATUSams_wms0_4 auto:cdsdisk - - onlineams_wms0_5 auto:cdsdisk d01 nadg online cloneddisk_0 auto:none - - online invaliddisk_1 auto:none - - online invalid

Situations involved array configuration issues or HBA configuration problems can also cause the 'udid_mismatch' flag to appear, usually in tandem with other DMP issues.

If the environment is working normally, and you do not experience any functional issues when working with 'udid_mismatch' flagged LUNs, and the LUNs in question are create through some form of LUN duplication procedure, then there is no issue and you do not need to pursue the issue further.

For environments where you are not using cloned LUNs and you are experiencing other issues such as paths not being multipathed correctly, or other DMP issues, please contact Technical Support for further investigation.