The SAN Volume Controller initialization
includes a process 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 SAN Volume Controller 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 using the
svctask detectmdisk command-line
interface
(CLI) command or the
Discover MDisks function
from
the
SAN Volume Controller Console.
The
svctask detectmdisk CLI command and the
Discover
MDisks function
have the cluster rescan the fibre-channel network. The rescan discovers
any
new MDisks that might have been added to the cluster and rebalances
MDisk
access across the available controller device ports.
Note: Some storage systems do
not automatically export LUs to the SAN Volume Controller.
Guidelines for exporting LUs
Ensure that
you are
familiar with the following guidelines for exporting LUs to the SAN Volume Controller:
- When you define the SAN Volume Controller 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 SAN Volume Controller.
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 SAN Volume Controller until
the array initialization and format is complete.
If you add a LUN to an MDisk group before the array initialization
format
is complete, the MDisk group goes offline. While the MDisk group is
offline,
you cannot access the VDisks that are in the MDisk group.
- When
you export an LU to the SAN Volume Controller,
the LU must be accessible through all ports
on the storage system that are visible to the SAN Volume Controller.
Important: The LU must be identified
by the same logical unit number (LUN) on all ports.