System initialization includes a process that is called discovery.
The discovery process systematically recognizes all visible
ports on the SAN for devices that identify themselves as storage systems and the number of logical
units (LUs) that they export. The LUs can contain new storage or a new path for previously
discovered storage. The set of LUs forms the
managed disk (MDisk)
view.
The discovery process runs when ports are added to or deleted from the
SAN and when certain error conditions occur. You can also manually run the discovery process by using the
detectmdisk command-line interface (CLI) command or the
Discover
MDisks function from the
management GUI.
The
detectmdisk command and the Discover MDisks function have
the clustered
system rescan
the Fibre Channel network. The rescan discovers any new MDisks that were added to the system and rebalances MDisk
access across the available storage-system device ports.
Note: Some storage systems do not automatically export
LUs to the system.
Guidelines for exporting LUs
Ensure that you are familiar with the following guidelines for exporting LUs to the
system:
- When you define the system as a host object to the storage systems, you must include all ports
on all nodes and candidate nodes.
- When you first create an LU, you must wait until it is initialized before you export it to the
system.
Attention: Failure to wait for the LUs to initialize can
result in excessive discovery times and an unstable view of the SAN.
- Do not present new LUs to the system until the array initialization and format is
complete. If you add a LUN to a storage pool before the
array initialization format is complete, the storage pool goes
offline. While the storage pool is offline, you cannot access
the volumes that are in the storage
pool.
- When you export an LU to the system, the LU must be accessible through all ports on the
external storage system that are
visible to the system.
Important: The LU must be identified by the same logical unit number (LUN) on all
ports.