Read Errors After Primary Member of Mirror Set Fails

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If the system experiences a failure on a mirror set, Windows NT will breakthe mirror and orphan the faulty drive. There may be a situation where baddata is passed back to applications after breaking the mirror. This cancause a variety of problems, such as application problems and read mediaerrors on a healthy disk.

In addition to symptoms

  • A server with hot pluggable disk system (for example: Compaq, HP)
  • Mirror set created in the disk system
When you unplug the mirror disk while online from the mirror set (forexample, hardware failure), a warning message is received that the mirrorset is broke. The server and the original disk are functioning correctly.After you shut down the server, replace the mirror disk and then restartthe system, you may encounter file corruption with the original disk. DiskAdministrator may report a healthy status for the mirror set.
Although one of the mirrored disks was orphaned because of hardwarefailure, users continue to use the system without replacing the failed diskand re-creating the mirror set. During this time, disk I/O is suppose to beperformed only from the partition of the healthy disk.

If an application requests data from the disk, and a read I/O error isencountered on the healthy disk, Ftdisk.sys erroneously retrieves data fromthe orphaned disk, which results in unreliable data from the orphaned diskbeing returned to the application as reliable data.
To resolve this problem, obtain the latest service pack for Windows NT 4.0 or Windows NT Server 4.0, Terminal Server Edition. For additional information, click the following article number to view the article in theMicrosoft Knowledge Base:
152734 How to Obtain the Latest Windows NT 4.0 Service Pack


To work around the problem, before you shut down the server and replace thedisk, you should manually break the mirror set in Disk Administrator.

For additional information, please see the following article in theMicrosoft Knowledge Base:

120227Steps to Recover a Failed Mirrored System/Boot Partition
Microsoft has confirmed that this is a problem in Windows NT 4.0 and Windows NT Server 4.0, Terminal Server Edition. This problem was first corrected in Windows NT 4.0 Service Pack 4.0 and Windows NT Server 4.0, Terminal Server Edition Service Pack 4.
scsi dirty mirroring

Article ID: 194351 - Last Review: 10/10/2013 22:32:46 - Revision: 2.1

Microsoft Windows NT Server 4.0, Terminal Server Edition, Microsoft Windows NT Server 4.0 Standard Edition

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