Dell PERC controller learn cycle mode
Summary: This article provides information about the battery learn cycle, which is a battery calibration operation performed by the controller periodically to determine the condition of the battery. This operation cannot be disabled. ...
Symptoms
Note: This article is part of the Server Tutorials: "Raid and Disks" available here .
Note: Battery relearning refers to draining a battery in order to determine how long it holds a useful charge.
Table of Contents:
1. Battery Transparent Learn Cycle
A transparent learn cycle is a periodic operation that calculates the charge that is remaining in the battery to ensure there is sufficient energy. The operation runs automatically, and causes no impact to the system or controller performance.
The controller automatically performs the Transparent Learn Cycle (TLC) on the battery to calibrate and gauge its charge capacity once every 90 days. The operation can be performed manually, if required.
All PERC 8 (H310 - H710) and above have this feature. The list of RAID Controllers is available on this link.
Cause
2. Battery Learn Cycle
Battery Learn Cycle can be started manually or automatically. In addition, automatic learn cycles in the software utility can enabled or disabled.
If you enable automatic learn cycles, you can delay the start of the learn cycles for up to 168 hours (7 days). If you disable automatic learn cycles, you can start the learn cycles manually, and you can choose to receive a reminder to start a manual learn cycle.
You can put the learn cycle in Warning Only mode. In the Warning Only mode, a warning event is generated to prompt you to start the learn cycle manually when it is time to perform the learn cycle operation. You can select the schedule for initiating the learn cycle. When in Warning Only mode, the controller continues to prompt you to start the learn cycle every seven days until it is performed.
Note: In PERC H700 and previous, virtuals disks automatically switch to Write-Through mode when the battery charge is low because of a learn cycle. Once the battery charge is sufficient, Write-Back mode will be re-enabled.
Learn Cycle Completion Time Frame
The time frame for completion of a learn cycle is a function of the battery charge capacity and the discharge/charge currents used. The expected time frame for completion of a learn cycle is approximately seven hours and consists of the following parts:
- Learn cycle discharge cycle: approximately three hours
- Learn cycle charge cycle: approximately four hours
During the discharge phase of a learn cycle, the battery charger is disabled and remains disabled until the battery is discharged. After the battery is discharged, the charger is re-enabled.
When the learn cycle detects the battery can no longer store enough charge for 24 hours you will receive a "Predicted failure" message in the system logs, telling you the battery is near the end of it's useful life and needs to be replaced.
A "Battery failed" message during the learn cycle is considered normal, and can safely be ignored. The battery should return to a normal state within a few minutes.
A "Battery failed" message outside of the learn cycle would indicate the battery has reached the end of it's life and needs immediate replacement. Before replacement you should ensure the battery is correctly plugged in to the PERC controller. Having up to date PERC firmware can extend the useful battery life, and avoid miss-reporting of errors.
Resolution
3. Modifying the Battery Learn Cycle
The PERC 5, PERC 6, PERC H700/H800 battery learn cycle mode can be modified with OpenManage Server Administrator (OMSA) Command Line Interface (CLI).
The options are Warn and Auto
- On Auto mode the learn cycle runs every 90 days.
- On Warn mode the learn cycle is blocking from running, except for the first occurrence of the cycle.
The controller needs to run the learn cycle at least once to determine the actual capacity of the battery with accuracy. This first learn cycle will be scheduled to run 90 days after initial boot up, or after identifying a new battery. Even if the learn cycle is in warn mode the first learn cycle will run.
After the first learn cycle has been executed and the mode is set to Warn:
when the learn cycle is due, the controller Firmware issues a warning and the battery will be set to degraded state.
The commands to change the learn cycle mode are:omconfig storage globalinfo action=service_changelearnmode controller=0 battery=0 learnmode=warn
omconfig storage globalinfo action=service_changelearnmode controller=0 battery=0 learnmode=auto
If the learn cycle runs while is warn mode, verify this is not the first learn cycle for the current battery on the controller. This is expected.
If the customer wants to control the learn cycle execution and not suffer the mandatory first one at an unplanned time, execute the learn cycle manually ASAP and set the mode to warn.
Note: Dell recommends to run the learn cycle every 90 days.