This article was previously published under Q112555
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The mirroring process for Microsoft LAN Manager produces corruption onthe mirror of the boot volume, most noticeably with large (around 40MB)files. There are various symptoms. After unmirroring a drive, large filesand their directories may show evidences of corruption: inability to do adirectory on C:\PUBLIC when large files reside there, incorrect data onthe screen when you use the Type command to display a text file[ASCII 146]s contents.If the drive is unmirrored using FTSETUP, on reboot, CHKDSK finds a numberof corrupt files/directories and removes them from the former mirror.
Some casts of longs to shorts in FTDLL.DLL and FTSETUP.EXE caused sectorruns of greater than FFFF length to be copied incorrectly to the duplicatedrive during the mirroring process, escpecially when drives containing alot of data were mirrored.
Microsoft has confirmed this to be a problem in LAN Manager versions 2.1,2.1a and 2.2. A fix to this problem is in development, but has not beenregression-tested and may be destabilizing in production environments.Microsoft does not recommend implementing this fix at this time. ContactMicrosoft Product Support Services for more information on the availabilityof this fix.