3.9.2 Monitoring Storage Server Hard Disk Controller Batteries and Caching Mode

The hard disk controller in Exadata X4 and earlier systems periodically performs a discharge and charge of the controller battery. During the operation, the write cache policy changes from write-back caching to write-through caching.

Note:

This topic applies only to Exadata X4 and earlier systems, which use batteries to protect the disk controller cache.

Write-through cache mode is slower than write-back cache mode. However, write-back cache mode has a risk of data loss if the Oracle Exadata Storage Server loses power or fails. For Oracle Exadata System Software releases earlier than release 11.2.1.3, the operation occurs every month. For Oracle Exadata System Software release 11.2.1.3.0 and later, the operation occurs every three months, for example, at 01:00 on the 17th day of January, April, July and October.

• To change the start time for the learn cycle, use a command similar to the following:

  CellCLI> ALTER CELL bbuLearnCycleTime="2013-01-22T02:00:00-08:00"
  

  The time reverts to the default learn cycle time after the cycle completes.

• To see the time for the next learn cycle, use the following command:

  CellCLI> LIST CELL ATTRIBUTES bbuLearnCycleTime
  

  Oracle Exadata Storage Server generates an informational alert about the status of the caching mode for logical drives on the cell, similar to the following:

  HDD disk controller battery on disk controller at adapter 0 is going into a learn
  cycle. This is a normal maintenance activity that occurs quarterly and runs for
  approximately 1 to 12 hours. The disk controller cache might go into WriteThrough
  caching mode during the learn cycle. Disk write throughput might be temporarily
  lower during this time. The message is informational only, no action is required.
  

• To view the status of the battery, use a command similar to the following example:

  Note:

  If you are running Oracle Exadata System Software 19.1.0 or later, substitute /opt/MegaRAID/storcli/storcli64 for /opt/MegaRAID/MegaCli/MegaCli64 in the following command:

  # /opt/MegaRAID/MegaCli/MegaCli64 -AdpBbuCmd -GetBbuStatus -a0
  BBU status for Adapter: 0
   
  BatteryType: iBBU08
  Voltage: 3721 mV
  Current: 541 mA
  Temperature: 43 C
   
  BBU Firmware Status:
  Charging Status : Charging
  Voltage : OK
  Temperature : OK
  Learn Cycle Requested : No
  Learn Cycle Active : No
  Learn Cycle Status : OK
  Learn Cycle Timeout : No
  I2c Errors Detected : No
  Battery Pack Missing : No
  Battery Replacement required : No
  Remaining Capacity Low : Yes
  Periodic Learn Required : No
  Transparent Learn : No
   
  Battery state:
   
  GasGuageStatus:
  Fully Discharged : No
  Fully Charged : No
  Discharging : No
  Initialized : No
  Remaining Time Alarm : Yes
  Remaining Capacity Alarm: No
  Discharge Terminated : No
  Over Temperature : No
  Charging Terminated : No
  Over Charged : No
   
  Relative State of Charge: 7 %
  Charger System State: 1
  Charger System Ctrl: 0
  Charging current: 541 mA
  Absolute state of charge: 0 %
  Max Error: 0 %
   
  Exit Code: 0x00