IBM N Series, Hardware Manual

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IBM System Storage N series Hardware Guide
Normal approach
The storage download shelf process requires 5 minutes to download the code to all A shelf
modules. During this time, I/O can occur. When the download completes, all A shelf modules
are rebooted. This process incurs up to a 70-second disruption in I/O for the shelf on both
controller modules (when a firmware version before version 37 is run). This disruption affects
data access to the shelves regardless of whether multipath is configured.
When the upgrade of the A shelf modules completes, the process repeats for all B modules. It
takes 5 minutes to download the code (nondisruptively), followed by up to a 70-second
disruption in I/O.
The entire operation incurs two separate pauses of up to 70 seconds in I/O to all attached
storage, including Fibre Channel if present in the system. Systems that feature multipath HA
or SyncMirror are also affected. The
storage download shelf command is run only once to
perform A and B shelf module upgrades.
Alternative approach
If your system is configured as multipath HA, the loss of either A or B loops does not affect the
ability to serve data. Therefore, by employing another (spare) storage controller, you can
upgrade all your AT-FCX modules out-of-band. You remove them from your production system
and put them in your spare system to conduct the upgrade there. The pause in I/O then
occurs on the spare (nonproduction) storage controller rather than on the production system.
This approach does not eliminate the risk of latent shelf module failure on the systems in
which modules are being swapped in. It also has no effect on the risk of running different shelf
controller firmware, even if only for a short time.
20.2.4 Upgrading the AT-FCX shelf firmware during system reboot
This upgrade option is described here for technical clarity. Data ONTAP NDU requires all shelf
and disk firmware upgrades to occur before a system NDU operation is performed.
In systems that are incorporating AT-FC, AT-FC2, or AT-FCX shelf modules, including mixed
environments with LRC or ESHx modules, shelf firmware upgrade occurs automatically
during the boot process. System boot is delayed until the shelf firmware upgrade process
completes.
Upgrading all shelf modules entails two downloads of 5 minutes each along with two reboot
cycles of up to 70 seconds each. This process must be completed before the system is
allowed to boot, and results in a total delay in the boot process of approximately 12 minutes.
Upgrading shelf firmware during reboot suspends I/O for the entire 12-minute period for all
storage that is attached to the system, including the partner node in HA pair configurations.
20.3 Disk firmware NDU
Depending on the configuration, the N series allows you to conduct disk firmware upgrades
nondisruptively (without affecting client I/O). Disk firmware NDU upgrades target one disk at a
time, which reduces the performance effect and results in zero downtime.