shrink VM disk

  • 22 March 2021
  • 5 replies

HI Team

 under Prism we’ve created a few VM’s (windows), one of VM is our File Server, current configuration is IDE disk 1TB, (60GB OS, 900GB shared folders). probably is better to create one virtual disk 60GB on OS and the second virtual disk as storage (1TB) or more.

question is how to shrink current IDE disk from 1TB → 60GB, and if IDE should be change on SCSI disk, what Nutanix recommended?

  1. instruction to shrink disk
  2. IDE->SCSI

thanks Dariusz


Best answer by Sergei Ivanov 22 March 2021, 13:09

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Hi Dariusz,

we recommend to always use SCSI bus when possible, because it performs much better than IDE. For your example, i would go for a 60Gb OS SCSI disk and another (also SCSI) disk for the data storage.

It is impossible to shrink an existing vdisk. You can only increase the vdisks, but not shrink. 

To change from IDE to SCSI you can use the following article, section “How to change bus type or disk index”:


Thanks Sergey,

But is possible to change disk size by clone disk or something (before migration from IDE to SCSI)? it means my current 1TB is too big, I would like to reduction it for example 60GB? it’s only Windows 2019 OS, 1TB has two partitions 60GB (OS) and 940GB is unallocated. 

I thought operation clone or …

Userlevel 4
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That will not work, unfortunately. The cloning operation will not allow to specify the size and will automatically take the same size as the source disk.

All the storage space on Nutanix is thin provisioned, so it won’t matter that the disk is 1Tb in allocated size and only 60GB is used. Since it’s thin provisioned, only the used storage will be occupied.

If it’s important for you to keep the OS disk small, it will be probably better to build a new VM with correct settings and move the data to it. Also, you can build a new VM with 60Gb OS disk and then clone the disk with data from the previous VM as the 2nd disk to the new VM.


Sergie is correct,  Nutanix is thin provisioned, so if you’re not using won’t eat up space unless you’re using it.  

If you really want to play and learn more about resizing, you could create a new image and copy the data over.   If you go down this road as a science experiment, you’ll first need to reduce the size of the filesystem (through windows disk management), and then do some research on VBoxManage which is part of VirtualBox.  Another tool is  gparted.  Windows complains a lot with resizing vs something like Linux.  While not really applicable to Nutanix, knowing how to resize windows can be helpful to squeeze that laptop image on a smaller ssd/NVME, etc.

OK, thanks, as Sergei said before, if I used less data, 1TB as OS is not a big issue, I’ve left “big” disk and create the second disk for data.

Please you can close the ticket, thanks for the support