Automatic thinning of virtual disks with makeThin

Here I present my latest tool for ESX. An script that automatically converts thick virtual disks to thin.

It has been used for almost a year in my team across different centers and the storage savings are >50%.

makeThin Documentation

Happy thinning!

[Update 8/January/2013]
Victor was kind enough to create a fork of this program for ESXi. You can find all the info on https://github.com/terreActive/makeThin
[End of update]

PS: If you link the documentation/script, please link to this post or the blog. The location of the document on the back may change, the blog will not.


  1. Hi Ruben,
    I am trying to use makeThin on my ESXi 4.1 host but i get stuck at the Installation step; please see the output bellow:
    ~ # ls /opt
    ~ # . /opt
    ~ # . makeThin_source_code_v6.txt
    -ash: .: makeThin_source_code_v6.txt: not found
    What could be the problem?
    Many thanks!

  2. ~ # . makeThin_source_code_v6.txt

    This loads the functions into the shell (after loading, they can be used).

    However the function names are makeThin, cleanupSAFETMP and computeThin.
    Please read the section "How to use makeThin and its related programs"

    But in your case, I see you are in an ESXi. These functions, as they are, won't work there. For more info see the section "ESX requirements".

  3. There are coding errors in this script do not use it.

  4. Thank you very much! I've made a fork which works on ESXi.

  5. Anonymous24 May, 2013


    I get an error al line 69 : unexpected "done" (expecting "do")
    -> this line vmkfstools -U "$TODELETE" ; done;
    Running ESXi 5.1
    I am not a programmer, any help would be very much appreciated
    Thanks in advance

  6. Anonymous24 May, 2013

    PLs forget my above question - CR/LF (Windows) seemed to cause the problem.

  7. Thank you mate, you are a BOSS!!

  8. Is this still working on ESXi 6.5?
    Is there any documentation on how to use this files to convert my thick VM to thin?


    1. If you need only in a vm.
      Shutdown the VM and detach the disk. Login into ESX, clone your vmdks (all of them) to other folder. After, delete your original vmdks. Last step: clone your vmdks to the original directory

      You must use vmkfstools for each clone. This example is for the second clone:

      #vmkfstools -i firstCloneDst/yourdisk.vmdk originalDst/yourdisk.vmdk -d thin

      It's only a clone but using the -d option. For convert to thin

  9. > Is this still working on ESXi 6.5?
    Not sure. I never tested on that version.

    > Is there any documentation on how to use this files to convert my thick VM to thin?

    There was, but seems to be gone.

    If you just want to convert one VM, it may be easier to just clone it, selecting thin disks on the process (check documentation for more details).

    This script was intended for conversion of large amounts of VMs.