Write Cache Disabled on Sun StorageTek 6540 Arrays After Losing One AC Power Input

Asset ID:	1-72-1398972.1
Update Date:	2012-03-04
Keywords:

Solution Type Problem Resolution Sure

Solution 1398972.1 : Write Cache Disabled on Sun StorageTek 6540 Arrays After Losing One AC Power Input

Applies to:

Sun Storage 6540 Array - Version: Not Applicable to Not Applicable - Release: N/A to N/A
Information in this document applies to any platform.

Symptoms

The Sun StorageTek 6540 Cache will be disabled if AC power is lost to one of the two Power Supplies. This will result in a performance impact until AC power source to the affected Power Supply is restored.
This behavior is not documented in the documentation and can cause confusion as loosing one of the AC power inputs is typically not associated with having a disabled cache.

In Sun Storage Common Array Manager (CAM) several alarms will be received and both Batteries will get the Status "Unknown" and the Major Event log (MEL) will contain a line stating that the cache is disabled.

Alarm example from the CAM Browser User Interface (BUI):

Site :  ---hidden---
Agent :  ---hidden---
Agent Id : 84005f14
Severity : Critical
Category : 6540
Device Id : SUN.371-1807-01
Serial : ---hidden---
Part Id : SUN.371180901
Part Serial :  ---hidden---
Part Revision : N/A
Part Number : 371180901
Topic : Tray.85.PowerSupply.B
Event Type : ProblemEvent
Event Code : 63.66.1097
Event Date : 2011-12-29 13:58:14
Event Id : 1325167094391.84005f14.4239

Description:
Tray.85.PowerSupply.B is not receiving input power.


Probable Cause:
Power to one of the Power Supply/Fan Assembly FRUs has been lost.

Recommended Action:
Verify that the power switch on the component is in the on position.
Check that the plug is seated at both ends.
Verify that the wall circuit breaker is on.
Verify that the building is receiving power.

Example from the alarm.txt file in the supportData:

Alarm Id : alarm2
Severity : Critical
Type : 6540.ProblemEvent
Topic : Tray.85.PowerSupply.B
Event Code : 63.66.1097
Date : 2011-12-29 13:58:14
Device : 
Description : Tray.85.PowerSupply.B is not receiving input power.
State : Open
Acknowledged By : -
Auto Clear : Y
Aggregated Count : 0

Example from the storageArrayProfile.txt file in the supportData:

Battery: Tray.85.Battery.A
Status: Unknown
Age in days: 153
Days until replacement: 1017

Battery: Tray.85.Battery.B
Status: Unknown
Age in days: 153
Days until replacement: 1017

Example in the majorEventLog.txt file in the supportData:

Date/Time: Thu Dec 29 13:43:16 GMT 2011
Sequence number: 8763
Event type: 210A
Event category: Notification
Priority: Informational
Description: Controller cache not enabled or was internally disabled
Event specific codes: 0/0/0
Component type: Controller
Component location: Tray.85.Controller.A
Logged by: Controller in slot A

Date/Time: Thu Dec 29 13:43:20 GMT 2011
Sequence number: 8764
Event type: 3101
Event category: Notification
Priority: Informational
Description: AEN posted for recently logged event
Event specific codes: 6/3f/c7
Component type: Controller
Component location: Tray.85.Controller.A
Logged by: Controller in slot A

Date/Time: Thu Dec 29 13:43:20 GMT 2011
Sequence number: 8765
Event type: 280B
Event category: Notification
Priority: Critical
Description: Controller tray component failed
Event specific codes: 0/0/0
Component type: PowerSupply
Component location: Tray.85.PowerSupply.B
Logged by: Controller in slot A

Date/Time: Thu Dec 29 13:44:08 GMT 2011
Sequence number: 8766
Event type: 3101
Event category: Notification
Priority: Informational
Description: AEN posted for recently logged event
Event specific codes: 6/3f/c7
Component type: Controller
Component location: Tray.85.Controller.B
Logged by: Controller in slot B

Date/Time: Thu Dec 29 13:44:09 GMT 2011
Sequence number: 8767
Event type: 210A
Event category: Notification
Priority: Informational
Description: Controller cache not enabled or was internally disabled
Event specific codes: 0/0/0
Component type: Controller
Component location: Tray.85.Controller.B
Logged by: Controller in slot B

Changes

This can happen either by a AC Power Cord being not properly seated or a problem with the AC power source itself .

Cause

The Sun StorageTek 6540 Array does have two Battery Backup Units (BBU), each BBU consists of two individual batteries meaning that there are four batteries in total.
When one of the Power Supplies looses the AC input one battery in each BBU will get the "Unknown" status.
The Sun StorageTek 6540 Array firmware will flag both Battery Backup Units as "Unknown" and consequently disable the cache.

Solution

Make sure that both AC input cords are firmly seated and make sure that both AC power cords are having power.

Attachments

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