HP Surestore Disk Array 12h and FC60 - Manual (Page 247)

Managing Disk Array Capacity 247
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Assigning LUN Ownership
When a LUN is bound, you must identify which disk array controller (A or B) owns the
LUN. The controller that is assigned ownership serves as the primary I/O path to the LUN.
The other controller serves as the secondary or alternate path to the LUN. If there is a
failure in the primary I/O path and alternate links are configured, ownership of the LUN
automatically switches to the alternate path, maintaining access to all data on the LUN.
When assigning LUN ownership, consider the following:
• To ensure optimum performance, LUN ownership should be balanced between
controllers. This ensures that one controller is not overloaded with I/O requests, while
the other is idle.
• Controller ownership can be changed on an existing LUN without impacting its
operation. If you find that there is an imbalance between I/O path loads, you can change
the ownership of one or more LUNs to solve the problem.
Note
Does the primary path selected using LVM impact LUN ownership?
Yes. The primary I/O path established using LVM defines the owning controller
for the LUN. This may override the controller ownership defined when the LUN
was bound. For example, if controller A was identified as the owning controller
when the LUN was bound, and LVM subsequently established the primary path
to the LUN through controller B, controller B becomes the owning controller.
Selecting a RAID Level
C AUTION
RAID 0 does not provide data redundancy. It should only be used in
situations where high performance is more important than data protection.
The failure of any disk within a RAID 0 LUN will cause the loss of all data on
the LUN.. RAID 0 should only be used for non-critical data that could be lost
in the event of a hardware failure.
The RAID level you select for each LUN determines the method used to store data on the
disks. Once selected, the RAID level cannot be changed dynamically. If you want to change