Batteries
Each node canister in the control enclosure caches critical data and holds state information in volatile memory.
If power to a node canister fails, the node canister uses an internal battery to provide power to destage cache and state data to its boot drive, before performing an orderly shutdown. Once started, the shutdown operations run to completion even if the system power is restored during this time.
The battery has enough charge capacity to handle two back-to-back power failures. This means that normally the node canister can restart I/O operations immediately after repowering without waiting to recharge the battery, or requiring any operator intervention. If several power events occur in close succession such that the battery does not have enough charge for the node to save its internal state, the node remains in service until the battery is charged sufficiently.
Battery management
As a battery ages, it loses capacity. The battery in the node canister lasts at least five years before it cannot hold enough charge to support a successful node shutdown.
The batteries autonomously manage conditioning and learning cycles to maintain accurate state of health information. These cycles occur as determined by the battery’s internal logic and cannot be manually controlled. While they typically happen at regular intervals, the exact timing may vary depending on the battery’s condition.
When the battery capacity starts to degrade, the system posts an “End of Life Warning” event. At this point, the battery subsystem still has enough capacity to be able to support an unscheduled system power-down. Batteries should be replaced within six months of reporting an "End of Life Warning" event.
When a battery no longer has capacity to protect against a power loss event, it reports the “End of Life Fatal” event. If a battery reports an "End of Life Fatal" event, the node goes offline and the battery needs replacing to allow the node to exit from Service state and come online.
If a node canister’s battery fails, that canister goes offline and reports a node error. The remaining canister destages its cache and runs the I/O group in “write-through” mode until its partner canister is repaired and online.
The battery is externally accessible from the rear of the node canister and can be removed or replaced without removing the canister from the system.
The battery unit has a number of status LEDs, which are described in Node canister indicators.
To access information about the battery in the management GUI, select . On the System Hardware - Overview page, select Battery Module to display information about the battery module. To display information about the battery in the command-line interface, use the lsenclosurebattery command.