Asset ID:	1-72-1019150.1
Update Date:	2009-10-08
Keywords:

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Solution Type  Problem Resolution Sure

Solution  1019150.1 :   Microsoft Windows 2000 and 2003 Servers Disable Write Cache on Sun StorageTek[TM] 2500, 6000, and Flexline Arrays Causing Poor Performance  


PreviouslyPublishedAs
236021

Symptoms
Poor write performance on RAID devices or volumes attached to a Windows based server.
Arrays can log the following events, indicating that the caching behavior on the volume
has been requested to be changed by the host.

Date/Time: Tue Sep 04 10:28:54 EDT 2007
Sequence number: 8078
Event type: 3009
Event category: Command
Priority: Informational
Description: Mode for caching page 8 received
Event specific codes: 0/0/0
Component type: Volume
Component location: volume_name
Logged by: Controller in slot A

Resolution
This problem can be resolved by implementing the fix detailed in Microsoft KB 332023:


http://support.microsoft.com/kb/332023

Note: currently this document only mentions WIndows 2000 but it is also applicable to Windows
2003 as well.  Microsoft will be correcting this document to reflect this change.

This change was implemented by Microsoft in an effort to protect users from
data corruption.  Before the change it was too easy to use the internal cache of
a physical disk to increase performance. This exposed customers to potential
data loss in the event of a power outage because that cache was not backed up by
batteries.

The fix implemented by Microsoft treated all disks (logical and physical) the same 
The net result is that Windows based servers will attempt to disable  Write Cache on
any disk it sees including LUNs from an array with battery backup for it's controller cache.

A more detailed discussion on this subject can be found in this two part article:

http://searchstorage.techtarget.com/tip/1,289483,sid5_gci919227,00.html
http://searchstorage.techtarget.com/tip/0,289483,sid5_gci920473,00.html



Another possible work around for this problem is to modify the NVSRAM in 6xxx
and 25xx arrays so that they ignore the request from the Microsoft based host.  This is not
the best solution because it will be overwritten (reset) the next time that the
NVSRAM is updated.  But this may provide temporary relief for some customers.

To modify the NVSRAM using Common Array Manager 5.1.0 or higher:

Solaris: /opt/SUNWsefms/bin/
Windows: c:\program files\Sun\CommonArrayManager\Component\fms\bin
Linux: /opt/sun/cam/private/fms/bin

Command:
service -d array_name -c set -q nvsram region=0xF2 offset=0x17 value=0x01 host=0x1


Product
Sun StorageTek 2510 Array
Sun StorageTek 2530 Array
Sun StorageTek 2540 Array

Windows, write cache, disabled, storage

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