Veritas Volume Manager (VxVM) DDL may exclude EMC NDM related devices until EMC symdev identity reset operation is performed after completed NDM migration

Problem
 

The DELL/EMC NDM solution leverages VMAX SRDF replication technologies to move the application data from the source EMC storage array to the new target EMC storage array.

The Veritas Volume Manager (VxVM) Device Discover Layer (DDL) may exclude DELL/EMC NDM related devices following EMC NDM array migration, when the spoofing details have not been reset.

The DDL device exclusion can also be seen when upgrading to InfoScale 7.4.2 when NDM migrated devices are presented to the upgraded host.

 

Error Message

The following Device Discover Layer (DDL)  CLI command can be used to report any excluded devices:

# vxddladm list devices
<snippet>

Cause

Once the NDM migration is complete, it is vital the spoofing details for the NDM migrated LUNs are reset to avoid conflicts with other vendor Volume Management & Multi-pathing solutions, such as Veritas Volume Manager and Veritas Dynamic Mulit-pathing (DMP).

The purpose of NDM is to be transparent to the host. The user will need to be aware that the devices seen by the servers are not the "real" devices.

This "second wwn" will not cause issues with any host or replication, however it can sometimes lead to confusion while managing or troubleshooting the device.  


Related article available on DELL/EMC support site
:
Note: Devices Previously Used in NDM Have Two WWNs

https://www.dell.com/support/kbdoc/en-uk/000010796

Solution

Reset spoofing information for EMC NDM migrated SYMDEVs.

Note: The NDM migrated devices must be closed at the VxVM layer prior to updating the EMC SYMDEV attributes.

The following EMC Solutions Enabler (SYMCLI) command will remove any historical reference to the source EMC storage array:


Path:  /opt/emc/SYMCLI/bin

# symdev -sid SID reset -identity SYMDEV

Unique Disk Identifier (UDID)

Veritas Volume Manager (VxVM) refers to two UDID values, the UDID value returned by the DDL (Device Discovery Layer) which is the correct (true) UDID value of the LUN, whereas the UDID written on-disk can be from a different source.

The UDID structure consists of the Vendor ID (VID), Product ID (PID), Cabinet Serial Number (Cab_Serial_No) and Lun Serial Number (Lun_Serial_No - LSN) :

"VID , '_', PID , '_', CAB _Serial_No , '_', Lun_Serial_No "

As a result of clearing/resetting the spoofing information, this leads to the expected VxVM udid_mismatch flag being set, as the true UUID in the kernel differs to what is written on-disk.
 

The UDID information can be updated to make it appear as a STANDARD (STD) disk once again, using the command:

# vxdisk -c updateudid veritas-disk-access-name

The related VxVM disk groups can then be safely imported.