Hi, I have a win2k (mixed mode domain) with 4 DCS. One of these also acts an exchange 2000 server which uses 2 logical volumes from an MSA 2000 array. AD etc is stored on local drives. We experienced a problem last week when the raid array fell back to a redundant controller and this temporarily meant that the two logical drives were not visible to the server for around 5 minutes and a couple of reboots. The log records these Events as Type: Warning Event Source: Disk Event Category: None Event ID: 51 Date: 06/11/2009 Time: 11:46:23 User: N/A Computer: server1 Description: An error was detected on device \Device\Harddisk1\DR1 during a paging operation. Following these problems, the server “kerberos Key Distribution” service refuses to start with an “error.31 a device attached to the system is not functioning”. All other automatic start services (including net logon) are running and there are no DNS issues etc. All devices are also functioning but the two logical MSA disks are now numbered in the Windows Disk Management MMC as 2 and 4 and I suspect that they may have previously been identified as disks 1 & 2 and perhaps windows still sees this as an ongoing failure?? Replication has not been affected but obviously there are many audit failures in the security log relating to users and workstations presumably linked to the Kerberos issue. Attempting to manually start the kerberos service generates the following in the System Log. Event Type: Error Event Source: Service Control Manager Event Category: None Event ID: 7023 Date: 09/11/2009 Time: 09:46:55 User: N/A Computer: Server1 Description: The Kerberos Key Distribution Center service terminated with the following error: A device attached to the system is not functioning. DCDIAG passes all tests except “Advertising” and “Services” which I believe relate directly to the failure of Kerberos only. Any advice would be appreciated.