Veritas Volume Manager 5.1 SP1 Administrator"s Guide (5900-1506, April 2011)

Upgrading the array controller firmware online
Storage array subsystems need code upgrades as fixes, patches, or feature
upgrades. You can perform these upgrades online when the file system is mounted
and I/Os are being served to the storage.
Legacy storage subsystems contain two controllers for redundancy. An online
upgrade is done one controller at a time. DMP fails over all I/O to the second
controller while the first controller is undergoing an Online Controller Upgrade.
After the first controller has completely staged the code, it reboots, resets, and
comes online with the new version of the code. The second controller goes through
the same process, and I/O fails over to the first controller.
Note: Throughout this process, application I/O is not affected.
Array vendors have different names for this process. For example, EMC calls it a
nondisruptive upgrade (NDU) for CLARiiON arrays.
A/A type arrays require no special handling during this online upgrade process.
For A/P, A/PF, and ALUA type arrays, DMP performs array-specific handling
through vendor-specific array policy modules (APMs) during an online controller
code upgrade.
When a controller resets and reboots during a code upgrade, DMP detects this
state through the SCSI Status. DMP immediately fails over all I/O to the next
controller.
If the array does not fully support NDU, all paths to the controllers may be
unavailable for I/O for a short period of time. Before beginning the upgrade, set
the dmp_lun_retry_timeout tunable to a period greater than the time that you
expect the controllers to be unavailable for I/O. DMP retries the I/Os until the end
of the dmp_lun_retry_timeout period, or until the I/O succeeds, whichever
happens first. Therefore, you can perform the firmware upgrade without
interrupting the application I/Os.
For example, if you expect the paths to be unavailable for I/O for 300 seconds, use
the following command:
# vxdmpadm settune dmp_lun_retry_timeout=300
DMP retries the I/Os for 300 seconds, or until the I/O succeeds.
To verify which arrays support Online Controller Upgrade or NDU, see the
hardware compatibility list (HCL) at the following URL:
http://entsupport.symantec.com/docs/330441
Online dynamic reconfiguration
Upgrading the array controller firmware online
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