When a storage device contains a VMFS datastore copy, you can mount the datastore with the existing signature or assign a new signature.

Each VMFS datastore created in a storage disk has a unique UUID that is stored in the file system superblock. When the storage disk is replicated or snapshotted, the resulting disk copy is identical, byte-for-byte, with the original disk. As a result, if the original storage disk contains a VMFS datastore with UUID X, the disk copy appears to contain an identical VMFS datastore, or a VMFS datastore copy, with exactly the same UUID X.

ESXi can detect the VMFS datastore copy and display it in the vSphere Client. You can mount the datastore copy with its original UUID or change the UUID, thus resignaturing the datastore.

In addition to LUN snapshotting and replication, the following storage device operations might cause ESXi to mark the existing datastore on the device as a copy of the original datastore:

LUN ID changes

SCSI device type changes, for example, from SCSI-2 to SCSI-3

SPC-2 compliancy enablement