Discrepancy in volume size when you extend a volume with DISKPART

Had an issue come in today where the customer requested that one of their drives on SAN storage be expanded. They carved out the necessary disk space and expanded the LUN which was verified showing 430GB total on the array. Rescanned in Disk Management and showed the Unallocated Space. They then used diskpart to expand the D$ drive, disk management then shoed 430GBs.  However, properties still showed only 359GB. Diskpart list disk showed 430GB.

So why the discrepancy?  Well when you extend a volume with DISKPART it doesn't automatically extend the file system with it, so you need to do the following:


Microsoft DiskPart version 6.0.6001

Copyright (C) 1999-2007 Microsoft Corporation.

On computer: ServerX

DISKPART> sel vol d

Volume 1 is the selected volume.


DiskPart successfully extended the file system on the volume.

When that is completed, then you'll see all the space in the properties.  If you extend the volume via the MMC then this happens automatically for you behind the scenes.

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Comments (3)

  1. Christopher Beard says:

    I have a question. I got the error that the partition had been successfully extended but not the file system. I ran EXTEND FILESYSTEM and received a message: "Diskpart failed to extend the filesystem on the volume." Any idea how to resolve this issue? The drive I extended was 1TB and I extended it to 1976.56 GB so I didn't break the 2TB limit of a basic drive. What can I do?

  2. Jason says:

    I am looking at the same error as Christopher Beard ("DiskPart failed to extend the file system on the volume"). I have not yet come across any documentation regarding this error, but I suspect it is a corruption issue based on errors in eventvwr since extending the partition. Once a chkdsk completes, I will try extending the file system again.

  3. Chris says:

    This worked for me, Had two CSV’s that were not showing the full size after adding extra disks.

    Did the Diskpart Extend first, then diskpart extend filesystem


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