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

Managing Magnetic Disks
SCF Reference Manual for the Storage Subsystem—529937-008
7-24
Swapping Processors for a Disk
Swapping Processors for a Disk
The PRIMARY DISK Command (page 14-92) swaps the primary and backup
processors for a disk. The current primary processor becomes the backup processor,
and the backup processor becomes the primary processor, but the PRIMARYCPU and
BACKUPCPU values stay the same.
You typically swap processors for a disk when load balancing the system or preparing
for disk replacement.
PRIMARY DISK Consideration
For G06.10 and earlier RVUs, using the PRIMARY command to swap a disk to its
backup processor can affect the other disk processes using the same SACs.
An Example for G06.11 and Later RVUs
On G06.11 and later RVUs, SACs in the same topology branch are owned by both
processors. The PRIMARY command can change which processor actively uses a
SAC, but it does not change SAC ownership.
Because both processors in the same topology branch can use the same SAC, the
PRIMARY command does not create an access problem for the other processor.
In the figures that follow:
•
SACs and disks controlled by processor 2 are shaded.
•
Active paths, fabrics, and SACs are in bold.
•
Backup disk processes are represented with a prime mark: for example, $D0201'.
Note. To change the primary or backup processor values for a disk, stop all the disk paths
(STOP DISK command) or terminate the disk process (RESET DISK, FORCED). Then you
can alter the disk configuration with new PRIMARYCPU and BACKUPCPU values.
RVU ID Page
PRIMARY Command Function in G06.00 Through G06.10
8-8
PRIMARY Command Function in G05.00 and Earlier 8-11