Parallels virtual disk much larger on mac than windows is actually using

I’m using Parallels 9 on Mac OS X (Mavericks) to run Windows 7.
A couple of days ago I duplicated my Windows 7 virtual machine. Parallels spotted the duplicated machine when it started and offered to create a new MAC address. All looked good.

I uninstalled some software but Parallels was still using just as much disk space. Windows said it was using 64GB but Parallels and the folder size in Mac OS X reported 137GB. I wanted that free space back!

I searched the knowledge base but couldn’t find an answer. I then sent a long support request to Parallels complete with about 7 screenshots of various things and information that I thought might be related. Less than 12 hours later (great support!) they emailed back with the solution. Although I had no snapshots, it appears some snapshots from last year remained and that was what caused the problem. In case someone else is having the same problem, here is what they said:

[Parallels #1780846] Windows 7 Virtual Disk much larger in Mac/ Parallels than windows and can't reduce


Thank you for contacting Parallels Desktop Technical Support and taking some time to explain with us the concern.

Based on the details that you shared with us. We would like to recommend some troubleshooting steps/article that might help us on solving the concern.

Please follow the advanced troubleshooting part of the article below.

>ERROR: Unable to delete the snapshot

Warning: We strongly recommend to create a backup copy of your Virtual Machine before applying the solution below!
Please take into account the size of virtual machine comparing to free space on Macintosh HD.
Once you created a backup copy, please proceed with the following:
1. Locate your Virtual machine in Finder
2. Right click on the *.pvm file of your virtual machine -> choose Show Package Contents
3. In Mac OS X, go to Applications > Utilities and launch Terminal. Type the following but do not execute:
prl_disk_tool merge --hdd
4. Drag the *.hdd file into Terminal and drop it right next to "prl_disk_tool merge --hdd ". In Terminal you will see something like this:
prl_disk_tool merge --hdd /Users/Username/Documents/Parallels/Windows 7.pvm/Windows 7-0.hdd
Note: There should be a space between '--hdd' and 'Users/Username...'
5. Press Enter/Return key to run the command and merge the snapshots.
6. At the same directory (inside Virtual Machine's bundle) delete Snapshots.xml file

Afterwards, please try to shrink the Virtual Hard disk size or compress it.

>Compressing the Disk's%20Guide/33140.htm


15 responses to “Parallels virtual disk much larger on mac than windows is actually using”

  1. when i do step 5 terminal operations just hang at 20%. However, the hdd thats being merged is 307 gbs, but I would think after an hour the operation progress would have gone up beyond 20%; right? And what does deleting the snapshot xml do?

    1. It’s a long time since I did this but it might not be ‘hanging’ at 20%, maybe it’s just not updating progress in the way you’d expect. For example, 20% means step 2 out of 10 and step 2 takes most of the time.

      Check ‘Activity Monitor’ and see if you’ve any disk traffic. That might even be a low level of traffic (eg: not full speed you’d normally see disk access) but it will be a sign that it’s working. In which case, the solution may be to leave it longer. I’d suggest at least 8 hours (overnight?).

      If you’ve access to another mac, maybe you could copy the Virtual Machine to that and try the merge there whilst still being able to work.

      I imagine snapshots.xml helps Parallels know where to find snapshots and that once you’ve done all the other steps that file is safe to be deleted.

      PS – Make sure you’ve got a backup before doing this, like Parallels say you should!

  2. Wow ! Thanks a lot, I struggled on this, with a VM which refused to shrink from its 75 GB. I managed to halve its size thanks to your blog post. So great !

  3. excellent guide ! it works and help me saved 60gb of space . Well done
    Thousand thanks.

  4. I have two HDd files and they are 250gb, is that both hard drive they have the same name I wonder when I made my vitural files if it go doubled. Wish I could show someone it’s filling my start up disk.

    1. I think your best option is to ask the question on the parallels forums. There can be lots of reasons to have more than one .hdd file that are OK. Consider also, if you need the space, sometimes it can be simpler/faster/cheaper to buy a new bigger hard disk

  5. Worked like a charm! Thank you very much for this post!

  6. Steve, thanks for this, have used it before, however not that I try it i get the following
    -bash: prl_disk_tool: command not found
    any ideas?

    1. Perhaps it is no longer part of your ‘path’ to be started just by calling it’s name? If so perhaps you need to find it on your disk and call it directly (eg: cd /bin/some/place/you/find/it … then try calling it).
      Or, maybe you’ve not got parallels installed (I’m guessing parallels installs the utility).
      The parallels forums would be a good place to ask for help on this.

      1. Wow, thanks for the quick reply! I have tried the parallels site, they recommend uninstalling parallels and doing a clean install. There are several reasons why I would like to avoid this though, so I’m trying to find a workaround, perhaps to just install the utility or paste it where parallels expects to find it. Ideas? I will try to locate it on the disk, haven’t been messing in the package, so not sure why it would not be where I left it.

  7. Fantastic, the file shrank by 60GB! Thanks for posting this 🙂

  8. Thanks for this instructions. They were super easy to follow and help me reclaim 120 GB of space. More than I expected. Regards.

  9. thanks a lot, that works great!

  10. Hello,

    After doing this, window no longer boots. Has anyone had this problem? I use Windows 10, and Parallels Desktop 12 on a MacBook air (2014) OS Sierra.


  11. Very helpful. Thank you

Leave a Reply

Your email address will not be published. Required fields are marked *

Search this site

Free apps

  • – Your birthday or other celebration date based on [years on other planets] / [how many seconds/days] / [how far you’ve travelled around the sun]
  • – Calculates the combination and how many 1st, 2nd, large 1st and large 2nd class Royal Mail stamps you need on large envelopes and packets

Recent posts