Reduce size of VM by merging snapshots.

M

Mike Boreham

Pro
If you right click the .pvm file -> Show Package Contents, then right click the hdd file -> show package contents, you may see something like I have after a few months: Screen Shot 2017-04-15 at 08.52.25.png
These can all be merged in a single smaller hds file using the Parallels Merge tool.
Open a Terminal window and type (or copy and paste):
prl_disk_tool merge --hdd
Then type one space
Then drag the hdd file (the one after the first 'show package contents' on the pvm file) into the Terminal window
Press enter, password etc
The merge tool will combine all the separate hds files into one smaller one.
In my example above the pvm file was reduced from 98 Gb to 81 Gb. I have often seen bigger reductions.
This situation arises from use of snapshots.
It is now a regular maintenance activity for me. It has never caused any problem for the VM.
I have not seen it recommended by Parallels, although I found the merge tool in a Parallels KB.
If you search the Parallels KB database for "merge" the above tool appears as the solution for a number of problems, but is never mentioned as a simple way of reducing the VM size.
 
Hi Mike Boreham,
We are happy to see your active participation. We would also suggest you to take a backup of the pvm file before merging the snapshots. You can refer this article for clear instructions.
 
Ajith@Parallels said:
Hi Mike Boreham,
We are happy to see your active participation. We would also suggest you to take a backup of the pvm file before merging the snapshots. You can refer this article for clear instructions.
Click to expand...

Indeed! Multiple back ups are second nature to me so I didnt mention that.
The reason I posted it that this process is a great way of saving space on a perfectly healthy VM, but only seems to appear in Parallels documentation as a method of solving specific problems.
 
Mike Boreham said:
Indeed! Multiple back ups are second nature to me so I didnt mention that.
The reason I posted it that this process is a great way of saving space on a perfectly healthy VM, but only seems to appear in Parallels documentation as a method of solving specific problems.
Click to expand...
We understand the but backing up the VM before merging the snapshot files is an essential step as if anything happens in the middle of merging snapshots it might corrupt the VM completely. We will also forward your feedback to the management.
 
I had originally set up the hard drive for my VM as an expanding version of about 80GB. It had been running out of space but I could not use the Settings functions to increase it. I would get a notice that the drive had snapshots and when I went to the manage snapshots functions, I was told that there were no snapshots. I had no recollection of ever having set up a snapshot myself, so that seemed true enough. But still, I'm in this typical, stupid, self-defeating software cycle.

Anyway, I came to this forum and searched on snapshots and found this thread. How brilliant. The package contents revealed 3 huge snapshots. I did a backup and ran this utility as described. The pvm file went from about 190GB to 80GB. As well, the Settings dialog to manage the hdd no longer complained about inaccessible snapshots, and I was able to increase the expanding disk size again. As well, the VM and its apps started up much more quickly, naturally enough.

This solution is brilliant and should get more visibility.
 
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