Tip

Using Diskpart to create, extend or delete a disk partition

One highly useful utility for Windows 2000/XP/Windows Server 2003/Windows Server 2008 users is the Disk Partition Utility, aka Diskpart, a command-line interpreter designed as a disk management tool.

In a recent article, I showed you how to use Diskpart to scan for newly added disks. But Diskpart can also be used to create, delete and resize hard drive partitions as well as assign or reassign drive letters.

Note: Any text in parentheses are comments only; they should not be typed along with any commands given.

Create a partition in Windows with Diskpart. Using Diskpart to partition your disk is very beneficial for increasing the I/O performance of hard disks newly added to a RAID array. The documentation for many server applications, such as Microsoft Exchange Server, actually goes so far as to recommend that you should use Diskpart to create your Primary or Extended partitions. (A primary partition an be used as the system partition; an Extended Partition can only be used for additional logical drive assignments.)

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To create a partition:

  1. At a command prompt, type: Diskpart.exe
  2. At the DISKPART prompt, type: LIST DISK (Lists disks found. Make note of the drive number you wish to manipulate.)
  3. At the DISKPART prompt, type: Select Disk 1 (This selects the disk; make sure to type in the disk number from step 2.)
  4. At the DISKPART prompt, type: CREATE PARTITION PRIMARY SIZE=10000
    (Change the word PRIMARY to EXTENDED to create an extended partition.) (If you do not set a size (in MB), such as the above example for 10 GB, then all available space on the disk will be used for the partition.) (Seriously consider adding the following option to the end of the above command if you are using RAID (especially RAID 5) to improve disk I/O performance: ALIGN=64)
  5. At the DISKPART prompt, type: ASSIGN LETTER=D (Choose a drive letter not already being used.)
  6. At the DISKPART prompt, type: Exit
  7. Use the Command Prompt format command, Disk Administrator or any disk format utility to format the drive (typically using NTFS, of course).

Extend a partition in Windows with Diskpart. When it comes to adding space to a partition or volume, this method is superior to configuring Dynamic Disks. Dynamic Disk extensions only concatenate the newly added space, meaning they merely add the disk space to the "end" of the original partition without restriping the data.

Concatenation isolates performance within each partition and does not offer fault tolerance when the partition is configured in a RAID array. Diskpart allows you to restripe your existing data. This is truly beneficial when the partition is set up in a RAID array, because the existing partition data is spread out across all the drives in the array, rather than just adding new space to the end (like Disk Administrator).

Microsoft's "official" position is that that you cannot use Diskpart to extend your system or boot partition. However, this tip on increasing the capacity of your system volume, suggests otherwise.

Note: If you try it or any other method, make sure you have a full backup.

To extend a partition:

  1. Verify that contiguous free space is available on the same drive and that free space is next to the partition you intend on extending (with no partitions in between).
  2. At a command prompt, type: Diskpart.exe
  3. At the DISKPART prompt, type: Select Disk 1 (Selects the disk.)
  4. At the DISKPART prompt, type: Select Volume 1 (Selects the volume.)
  5. At the DISKPART prompt, type: Extend Size=10000 (If you do not set a size, such as the above example for 10 GB, then all available space on the disk will be used.)
  6. At the DISKPART prompt, type: Exit

Note: It is not necessary, but I normally reboot the server to make sure all is well from a startup standpoint.

To delete a partition in Windows with Diskpart: (Note: You cannot delete an active system or boot partition or a partition with an active page file.)

  1. At a command prompt, type: Diskpart.exe
  2. At the DISKPART prompt, type: Select Disk 1
  3. At the DISKPART prompt, type: Select Partition 1
  4. At the DISKPART prompt, type: DELETE partition
  5. At the DISKPART prompt, type: Exit

To wiping (or zero) a disk:
This operation deletes all data on the disk

  1. At a command prompt, type: Diskpart.exe
  2. At the DISKPART prompt, type: Select Disk 1
  3. At the DISKPART prompt, type: CLEAN ALL (The CLEAN ALL command removes all partition and volume information from the hard drive being focused on.)
  4. At the DISKPART prompt, type: Exit

Final note: Here are four important things to keep in mind regarding Diskpart.

  • Do not use DISKPART until you have fully backed up the hard disk you are manipulating
  • Do not use DISKPART on dynamic disks
  • Check with your disk vendor before using Diskpart
  • Install the Windows Resource Kit to get the Diskpart utility

TABLE OF CONTENTS
- Introduction
- Diskpart: A command-line for manipulating disk partitions in Windows
- Diskpart utility scans for newly added disks
- Diskpart: Create, extend or delete a partition

About the author:
Tim Fenner (MCSE, MCSA: Messaging, Network+ and A+) is a senior systems administrator who oversees a Microsoft Windows, Exchange and Office environment, as well as an independent consultant who specializes in the design, implementation and management of Windows networks.

This was first published in January 2007

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