H203202: Cache might be disabled during battery learn cycle - IBM System Storage DS3500, DCS3700, DS3950, and DS5020



Source

RETAIN tip: H203202

Symptom

In some rare instances, the IBM System Storage DS3500, DCS3700, DS3950 and DS5020 subsystems running controller firmware versions 7.75.11.00, 7.77.18.00 or 7.77.19.00 could disable write cache and go into write through mode for a period of approximately four to six hours during a battery learn cycle. This can cause performance impacts for certain solutions.

The write cache will become enabled again once the battery learn cycle has recharged the battery back to its minimum required level. There is no issue with the battery itself and it does not need to be replaced.

Affected configurations

The system may be any of the following IBM servers:

  • DCS3700 Storage Subsystem, type 1818, any model
  • DS5020 Disk Controller (1814-20A), any model
  • IBM System Storage DS3512, type 1746, any model
  • IBM System Storage DS3524, type 1746, any model
  • IBM System Storage DS3950 Express, type 1814, any model

This tip is not software specific.

This tip is not option specific.

The following system firmware level(s) are affected:

  • 75.11.00
  • 77.18.00
  • 77.19.00

Solution

This is fixed in controller firmware 7.77.20.00 and higher which can be downloaded from:

Additional information

Two primary functions that are performed on a battery by the subsystem are the maintenance cycle and the learn cycle. The maintenance cycle is used to recharge a battery that has drained some of its normal charge over a period of time. The learn cycle is the method used to calibrate the battery charge level.

In rare instances, when the learn cycle starts during a particular point in the maintenance cycle, the initial battery charge level may be unreliable. This combination of events may cause the cache to become disabled. The cache will be re-enabled once the controller has recharged the battery back to a minimum required level. The period of disablement could last approximately four to six hours. There is no issue with the battery itself and it does not need to be replaced.

The Major Event Log (MEL) messages that may be seen are:

  Enclosure 0, Slot A A needs attention condition has been raised by the controller firmware.

Enclosure 0, Slot B Write-back caching forcibly disabled

Enclosure 0, Controller 1, Slot 1 Low battery capacity

Enclosure 0, Slot A Controller cache not enabled or was internally disabled

Enclosure 0, Slot B Controller cache not enabled or was internally disabled

Enclosure 0, Controller 2, Slot 2 Low battery capacity

Enclosure 0, Controller 1, Slot 1 Learn cycle for battery started

Enclosure 0, Controller 2, Slot 2 Learn cycle for battery started

All of these will be informational except for the message that states "Write-back caching forcibly disabled", which will be a critical message.

Applicable countries and regions

 


Document id:  MIGR-5088114
Last modified:  2011-09-22
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