Surpassing the 26 Drive Letter Limitation in Windows

Windows assigns alphabetical letters to the volumes of storage/hard disk for easier identification and accessibility for the end user. However,  what if you have volumes of storage more than 26? Well, to address that Windows made Drive Letters are not the only way of accessing different volumes.

Drive Letter Assignment Algorithm:

1. Assign the drive letter A: to the first floppy disk drive (drive 0), and B: to the second floppy disk drive (drive 1).
2. Assign a drive letter, beginning with C: to the first active primary partition recognized upon the first physical hard disk.
3. Assign subsequent drive letters to the first primary partition upon each successive physical hard disk drive.
4. Assign subsequent drive letters to every recognized logical partition, beginning with the first hard drive and proceeding through successive physical hard disk drives.
5. Assign subsequent drive letters to any RAM Disk.
6. Assign subsequent drive letters to any additional floppy or optical disc drives.

You can still access the more than 26 volumes of storage using either Junction Points or Volume Mounts.  By using junction points, you can graft a target folder onto another NTFS folder or "mount" a volume onto an NTFS junction point. Junction points are transparent to programs.

About Mounted Drives:

1. A mounted drive is a drive that is mapped to an empty folder on a volume that uses the NTFS file system.
2. Mounted drives function as any other drives, but they are assigned drive paths instead of drive letters.
3. When you view a mounted drive in Windows Explorer, it appears as a drive icon in the path in which it is mounted.
4. Because mounted drives are not subject to the 26-drive-letter limit for local drives and mapped network connections, use mounted drives when you want to gain access to more than 26 drives on your computer.
5. For example, if you have a CD-ROM drive with the drive letter E, and an NTFS volume with the drive letter F, mount the CD-ROM drive as F:CD-ROM. You can then free the drive letter E, and gain access to your CD-ROM drive directly by using F:CD-ROM.
6. You can also use mounted drives when you need additional storage space on a volume. If you map a folder on that volume to another volume with available disk space (for example, 2 gigabytes), you extend the storage space of the volume by 2 gigabytes (GB). With mounted drives, you are not limited by the size of the volume in which the folder is created.
7. Mounted drives make your data more accessible and give you the flexibility to manage data storage based on your work environment and system usage.
8. These are additional examples by which you can use mounted drives:
• To provide additional disk space for your temporary files, you can make the C:Temp folder a mounted drive.
• When space starts to run low on drive C, you can move the My Documents folder to another drive with more available disk space, and then mount it as C:My Documents.
9. Use the Disk Management snap-in to mount a drive on a folder on a local volume. The folder in which you mount the drive must be empty, and must be located on a basic or dynamic NTFS volume.
10.  

Tools for Mounted Drives:

Subst.exe

• Associates a path with a drive letter. Used without parameters, subst displays the names of the virtual drives in effect.
• If you use Subst.exe to connect to a network resource using a Universal Naming Convention (UNC) path, the command runs successfully, but when you try to gain access to the new drive letter you receive an error message
• To work around this behavior, use the NET USE command to connect to network resources instead of the SUBST command

Preview Tools for NTFS Junction Points

 

Microsoft offers three utilities for creating and manipulating NTFS junction points:

Linkd.exe

• Grafts any target folder onto a Windows 2000 version of NTFS folder
• Displays the target of an NTFS junction point
• Deletes NTFS junction points that are created with Linkd.exe
• Location: Microsoft Windows 2000 Resource Kit

Mountvol.exe

• Grafts the root folder of a local volume onto a Windows 2000 version of NTFS folder (or "mounts" the volume)
• Displays the target of an NTFS junction point that is used to mount a volume
• Lists the local file system volumes that are available for use
• Deletes the volume mount points that are created with mountvol.exe
• Location: Windows 2000 CD-ROM in the I386 folder

Delrp.exe

• Deletes NTFS junction points
• Also deletes other types of reparse points, which are the entities that underlie junction points
• Aimed primarily at developers who create reparse points
• Location: Microsoft Windows 2000 Resource Kit

Junction Points Usage Recommendations

NOTE: Microsoft recommends that you follow these recommendations closely when you use junction points:

• Use NTFS ACLs to protect junction points from inadvertent deletion.
• Use NTFS ACLs to protect files and directories that are targeted by junction points from inadvertent deletion or other file system operations.
• Never delete a junction point by using Explorer, a del /s command, or other file system utilities that walk recursively into directory trees. These utilities affect the target directory and all subdirectories.
• Use caution when you apply ACLs or change file compression in a directory tree that includes NTFS junction points.
• Do not create namespace cycles with NTFS or DFS junction points.
• Put all your junction points in a secure location in a namespace where you can test them out in safety, and where other users will not mistakenly delete them or walk through them.

Feature Comparison to DFS

NTFS junction points are similar to the junction points in DFS because both are tools that are used to graft storage namespaces together. However, DFS junction points typically have more features than NTFS junction points. The following table lists some of the differences between DFS and NTFS junction points.

Collapse this tableExpand this table

Feature	DFS Junction Points	NTFS Junction Points
Junction point origin	Local network share	Local NTFS directory
Junction point target	Any network share	Any valid Windows 2000 local path
Recoverable	Yes	Yes (ChkDsk)
Persistable/portable state	Yes (Save as File)	Yes (explicit/copy/move/backup)
Multi-targeting	Yes	No
API	Yes	Yes
Graphical Tools	Yes	Minimal
Avail ability	NT Server 4.0 and Later	Windows 2000 w/NTFS

 

Resources:

• How to create and use NTFS mounted drives in Windows XP and in Windows Server 2003
• How to create and manipulate NTFS junction points
• Cannot Use Subst.exe with UNC Path
• Drive letter assignment