Battery operation in the node canister: 2145-SV2 and 2145-SA2

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The node canister in the node caches critical data and holds state information in volatile memory.

If power to the node canister fails, the node canister uses battery power to write cache and state data to its boot drive.

The battery is maintained in a fully charged state by the battery subsystem. At maximum power, the battery can save critical data and state information in two back-to-back power failures. If power to the node canister is lost, saving critical data starts after a five-second wait. (If the outage is shorter than five seconds, the battery continues to support the node and critical data is not saved.) The node canister stops handling I/O requests from host applications. The saving of critical data runs to completion, even if power is restored during this time. The loss of power might be because the input power to the enclosure is lost, or because the node canister is removed from the enclosure.

When power is restored to the node canister, the system restarts without operator intervention. How quickly it restarts depends on whether there is a history of previous power failures. The system restarts only when the battery has sufficient charge for the node canister to save the cache and state data again. A node canister with multiple power failures might not have sufficient charge to save critical data. In such a case, the system starts in service state and waits to start I/O operations until the battery has sufficient charge.

Two light-emitting diode (LED) indicators indicate the state of the battery:
  • Status LED - Green
  • Fault LED - Amber

See Procedure: Understanding the system status from the LEDs: 2145-SV2 and 2145-SA2 for more information.

Important: Although the system is resilient to power failures and brown outs, always install the enclosures in an environment that has reliable, consistent, and required AC power. Consider uninterruptible power supply units to avoid extended interruptions to data access.

Design parameters

Consider the following important design parameters:
  • The design life of the battery in the node is five years service after one year on the shelf.
  • The battery is automatically reconditioned every three months to measure the battery capacity. If a battery has a lower capacity than required (below the planned threshold), it is marked as End Of Life and should be replaced.
  • If a battery fails, the canister goes offline and reports a node error