Microsoft KB Archive/149927

= FTedit.exe: What You Can and Cannot Use It For =

Article ID: 149927

Article Last Modified on 11/1/2006

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APPLIES TO


 * Microsoft Windows NT Workstation 3.5
 * Microsoft Windows NT Workstation 3.51
 * Microsoft Windows NT Workstation 4.0 Developer Edition
 * Microsoft Windows NT Server 3.5
 * Microsoft Windows NT Server 3.51
 * Microsoft Windows NT Server 4.0 Standard Edition

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This article was previously published under Q149927



SUMMARY
Ftedit.exe is a Windows NT tool developed by Microsoft Product Support and included with the recent release of the Windows NT resource kit; it can also be obtained directly from Microsoft Product Support. The tool was designed to aid in the recovery of software RAID sets under Windows NT in certain circumstances. This article discusses how Ftedit.exe works and how it can help you solve certain kinds of Fault Tolerant (FT) problems.



MORE INFORMATION
Windows NT stores information pertaining to disks, drive-letter assignments, and RAID sets in the registry. The information is located in the following registry key:

In this key are one or more \Device\CdRomX values which hold information on CD-ROM drive-letter assignments, as well as an Information value, which is a REG_BINARY value, meaning it is data stored in a binary (rather than ASCII) format. The information stored in this registry value can be divided into data pertaining to hard drives and data pertaining to FT sets.

For each hard drive on the system, Windows NT stores the following information in the registry value mentioned earlier:
 * The disk signature (a 32-bit value found in the MBR)
 * A description of each partition on the drive, including:
 * Starting sector of the partition
 * Length of the partition (in sectors)
 * Drive letter assigned to the partition
 * Whether the partition is a member of an FT set

For each FT set on the system, Windows NT stores:
 * The type of FT set (mirror, stripe, volume set, etc.)
 * How many members the set has
 * A pointer showing the location of each partition in the set

All of the information in the registry is put there by Disk Administrator. All the information pertaining to drives and partitions is based upon drive information that Disk Administrator obtained by making system calls; this information is updated each time Disk Administrator is executed, so when new drives are added, the DISK key will be updated. All information pertaining to FT sets is put in when the FT set is created in Disk Administrator or when the FT set is updated.

What Ftedit.exe does is load the Information value from the DISK key, interpret it, and then allow you to manipulate that value and write it back to the registry. This is the ONLY thing that Ftedit does; the tool never touches or affects drive configuration. This fact puts limitations on what Ftedit.exe can do, including the following:
 * Ftedit cannot create FT sets. Ftedit can manipulate the FT set definition in the registry, but this is only part of what is involved in creating a new FT set.
 * Ftedit cannot add definitions for real drives. The tool will allow you to add dummy definitions that map to nonexistent drives, but only Disk Administrator can add the definition of a real drive (this task requires hardware information that Ftedit does not have).
 * Ftedit has no effect on hardware RAID. This is because hardware RAID sets are configured by a RAID controller and are perceived by Windows NT as a single physical drive.

However, Ftedit can help you in the following situations:
 * Disk Administrator no longer recognizes your FT sets (perhaps because you reinstalled Windows NT or ran emergency repair). Ftedit can be used to rebuild the FT set definition and allow the operating system to access the already existing FT set.
 * When you run Disk Administrator, you get error messages stating that your disk configuration has changed (for example, as a result of removing or swapping out drives on an existing system). Ftedit can be used to remove the descriptions of the nonexistent drives from the registry, thus stopping the error message.

For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

131658 Use Ftedit.exe to Recover Fault Tolerant Disk Configuration

Additional query words: 3.50 3.51 4.00

Keywords: KB149927

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