Version & Build: All

Symptom:

Server seems to freeze at regular intervals making the machine unresponsive for short periods of time (less than a few seconds).  In extreme cases, this can cause spool backlogs.

Cause:

modus™ updates information in the Registry.  These write-operations to the Registry are cached in a file called software.log.  By default, the OS will purge the cache and write the operations to the Registry hive every 5 seconds for Windows Server 2003 or every 5 minutes Windows 2000 Server.

During these intervals, the system appears to freeze.  This behavior is not normal. The root cause is usually a poorly configured RAID controller whereby the Windows operating system is installed with a RAID array.

Solution:

If you use a RAID array for your OS drive with the RAID mode set to writethrough mode instead of writeback mode, by default, the controller only sends an acknowledgement of a disk-write operation after the disk-write has completed.  In the example above, no disk-write operations would be acknowledged until the RAID controller has finished purging the cache file and has merged it into the Registry hive.  Therefore, it is recommended that the RAID controller on the OS drive be set to use writeback mode, which sends an acknowledgement before the write-operation is complete.  This ensures faster response.

For additional information, please consult the IBM Systems Software Information Center article Understanding write-cache mode for logical drives.