a) Please read the information in this Flash very carefully. The information is intended to help avoid potential data loss.
b) Please note that your IBM Storwize V7000 Unified system could be exposed to the issue described in this Flash even if you have upgraded to IBM Storwize V7000 Unified V1.4.2.x or higher. Accordingly, you should follow the instructions herein to avoid this issue.
For the systems that have (or once had) IBM Storwize V7000 Unified V1.4.1.x loaded, there are two potential issues related to file system disks (a.k.a Network Shared Disks or NSDs). If you are exposed to one of the issues then there is a chance you are also exposed to the other issue:
1) NSD server misconfiguration:
The file system disks (a.k.a Network Shared Disks or NSDs) are improperly configured when the file system disks or the file systems are created or modified.
This misconfiguration will cause the I/Os to be re-routed via the 1 Gbps Ethernet direct connection between the file modules (mgmt0) when there are FC (Fibre Channel) link failures between the file module and IBM Storwize V7000 storage.
This can also impact recovery of the system in the event of a file module or FC link failure.
2) NSD to VDISK mismapping:
Also, on creation of file system disks or file systems, the file system disks (a.k.a Network Shared Disks or NSDs) can get incorrectly mapped between the IBM Storwize V7000 Unified and the V7000 storage backend. This file system disk mismatch does not cause any issue during normal file system access operations. However any activities on the affected system that involves file system disk removal (like “rmdisk” or “rmdisk –cleanup” or reducing the file system size) can cause data loss.
To avoid potential data loss, users SHOULD NOT do either of the following on a system affected by this mismapping issue (Please refer to the ‘Diagnosing the problem’ section to find out if your system is affected):
a) Do not remove any file system disks (NSDs) by running CLI commands such as “rmdisk” or “rmdisk –cleanup”, even if the disk is free (i.e. not part of any file system).
b) Do not reduce size of any file system.
See more details here