The Problem with Drive Letters
Ever since the days of MS-DOS, Microsoft Windows has relied on a rigid alphabetical system to organize storage drives. The primary hard drive is always C:, the CD-ROM drive is usually D:, and USB flash drives are assigned letters like E: or F:.
For a standard home user with a single hard drive, this system works perfectly. However, if you are a systems administrator managing a massive corporate database server, this system breaks down completely. A massive server might have forty different hard drives plugged into it to store terabytes of customer data. Because the English alphabet only has 26 letters (and A and B are historically reserved for floppy disks), you will literally run out of drive letters.
To bypass the 26-letter limitation, Windows allows you to “mount” a physical hard drive directly inside an empty folder on the C: drive instead of giving it an alphabet letter. To create, manage, and delete these sophisticated storage architecture links from the command line, you must use the mountvol command.
Step 1: Open the Command Prompt
Because you are manipulating the core storage architecture of the operating system, you must run this tool with administrator privileges.
- Press the Windows Key, type
cmd. - Right-click on Command Prompt and select Run as administrator.
Step 2: Listing the Volumes
Before you can mount a new hard drive to a folder, you need to find the hard drive’s true mathematical identity. Behind the scenes, Windows does not care about the letter “C.” It tracks hard drives using a massive, terrifying alphanumeric string called a Volume GUID (Globally Unique Identifier).
To see the GUID of every single hard drive physically attached to the motherboard, run the command with no flags.
mountvol
The terminal will output a list of paths that look like this:
\\?\Volume{b3a8e9c4-0f2d-41a6-9d3e-8c7f5b2a1c09}\
Below each massive GUID, it will show you where that drive is currently mounted (e.g., C:\). If you plugged in a brand new, unformatted 5-terabyte hard drive, it will show the GUID, but say “*** NO MOUNT POINTS ***”.
Step 3: Mounting a Drive to a Folder
Assume you want to dedicate that new 5-terabyte hard drive entirely to storing the company’s SQL database backups. Instead of giving it the letter “D,” you want it to seamlessly appear as a folder on the C: drive.
First, use the mkdir command to create a completely empty folder on your C: drive.
mkdir C:\DatabaseBackups
Now, use the mountvol command to link the new folder to the new hard drive’s GUID.
mountvol C:\DatabaseBackups \\?\Volume{b3a8e9c4-0f2d-41a6-9d3e-8c7f5b2a1c09}\
The command executes silently. If you open the graphical Windows File Explorer and navigate to C:\DatabaseBackups, it will look like a normal folder, but it is actually a portal. Any file you drop into that folder is instantly saved to the physical 5-terabyte hard drive, completely bypassing the C: drive’s storage capacity.
Step 4: Removing a Mount Point
If you are upgrading the server and need to unplug the 5-terabyte hard drive to move it to a new machine, you cannot just rip the cable out. You must safely sever the software link between the C: drive folder and the physical drive.
You use the /d (delete) flag, specifying the exact folder you want to disconnect.
mountvol C:\DatabaseBackups /d
The link is instantly severed. The hard drive is now completely invisible to the operating system, and you can safely physically unplug it from the server. By mastering mountvol, you can build massively scalable server architectures that are completely immune to the historical 26-letter limit of the Windows operating system.