SCF Reference Manual for the Storage Subsystem (G06.27+, H06.04+)

Disk Load Balancing
SCF Reference Manual for the Storage Subsystem—529937-008
8-6
Disk Load Balancing on G06.10 and Earlier RVUs
Disk Load Balancing on G06.10 and Earlier
RVUs
Understanding SAC Ownership
On G06.10 and earlier RVUs each SAC is owned by a processor. A mirrored volume
can communicate with its processors through up to four SACs. These events can
cause SAC ownership to change:
•
A hardware failure along an active data path to that SAC.
•
A PRIMARY command on a started disk.
•
A processor failure or halt on a primary processor.
How a disk process responds to a loss of SAC ownership depends on the RVU:
Guidelines for G06.10 and Earlier RVUs
•
The disk load balance within an enclosure should be one-sided. Ideally, each
enclosure should have one primary processor that:
°
Runs all disk processes managing disk volumes in that enclosure
°
Owns all SACs in that enclosure
•
When you use the PRIMARY DISK command and it results in a SAC ownership
change, all the other disks that are actively using that SAC are affected.
Topology Branch Example for G06.10 and Earlier RVUs
The group 03 topology branch includes processors 4 and 5 in the group 03 processor
enclosure and the three I/O enclosures attached to it (groups 31, 32, and 33). The disk
processes are configured as follows:
•
Processor 4 owns the shaded SACS and manages the primary disk processes that
are running in the shaded disks.
•
Processor 5 owns the white SACs and manages the primary disk processes that
are running in the white disks.
RVU Response Page
G06.11 and later SACS are no longer exclusively owned. This is no
longer an issue.
--
G06.00 through G06.10 The disk process switches its primary process to the
alternate processor.
8-8
G05.00 and earlier The disk process tries to switch to the alternate path 8-11