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I've been trying to extract a series of compressed files - total ~50GiB (uncompressed) - to a hard disk with about 55GiB of free space.

Because this is a slow hard drive and with limited capacity, and since the content is highly compressible, I thought it would be a good idea to extract it to a new folder with NTFS compression enabled.

Now, as the extraction progresses, if I right-click the folder at any given moment to see its properties, it'll report the correct disk usage (e.g. "size 4.5GiB; size on disk 2.65GiB"). But, if I right-click the drive, the properties window will report a much larger increase reported as "used space" - in fact, a little over than the sum of "size" and "size on disk".

And this goes up to the point where the extraction fails because Windows reports the disk is full.

After some research I found a comment in the microsoft forums:

This problem has to do with a known Windows 10 bug. When you copy a file to a NTFS folder that has compression enabled, the drive will use twice the space required and won't relinquish that until a reboot of the drive.

This looks bizarre enough because it appears to defeat much of the purpose of transparent compression IMO. But okay, at the end of the day what I want to know is if there's a way around this.

I tried suspending in the middle of extraction with Process Hacker, taking the disk "Offline" and then back "Online" via the Disk Manager (diskmgmt.msc) and resuming the process. The "Used space" number is then reported correctly, but the extraction fails.

Is there an actual solution?

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2 Answers 2

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I just ran into this situation myself, and was able to work around it and get the space back without a reboot.

One caveat, I had enough space to uncompress the files and recompress them.

Also note that I found that if I copied a compressed file to a different compressed folder, that file took up nearly 4 times as much space as expected. After uncompressing and recompressing the file size was normal and the drive free space agreed.

SO I tried uncompressing the files in the first compressed folder then copying them to the second compressed folder, and they took up twice the expected space. Again, uncompressing the files and recompressing them corrected the space issues.

This is a surreal bug. I mean when you watch the drive space go UP as you uncompress files, that is very strange.

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  • Hey. I had completely forgotten about this question; but in fact I found a way to decompress all files without the need to have enough space. See the answer I just added. Have my upvote, anyway.
    – Marc.2377
    Commented Aug 1, 2019 at 23:02
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The steps I used to work around the problem were:

  1. Disable NTFS compression on the target folder
  2. Begin extraction
  3. Monitor disk space usage and Suspend (freeze) the working process that is performing the decompression when the disk space is near full
  4. Select all decompressed files, except the last one; right-click them and enable NTFS compression
  5. Wait until they are NTFS-compressed
  6. Resume execution of the suspended process
  7. Keep doing steps 3 - 6 until all files have been extracted
  8. Finally, re-enable NTFS compression on the target folder.

And this is how I managed to install Call of Duty: Modern Warfare Remastered.

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