Exchange / SQL transaction logs if not handled properly can be the cause of your disk suddenly filling up and thereby potentially causing issues.

1. Check if you've enabled the "Truncate Logs" option from the VSS Settings screen in VM Backup. If the tools are failing to deploy, please take a look at this article.
   
   
2. Ensure that the backup completed without any warnings for this virtual machine. If you're getting a warning, please take a look at this article.
   
   
3. Ensure you're running the latest version of VMware Tools inside the VM. You can check the latest version by following this link.
   
   
4. [Exchange] If you notice the Altaro VM tools are going back to 'Required' instead of 'Installed'. Please take a look at this article.
   
   
5. [SQL] Ensure you're using a Simple Recovery Model. Please take a look at this article for more information.
   
   
6. [Exchange] If you are running Exchange on a Server 2008 R2 VM, kindly contact the support team for help.
   
   
7. Please check for any Windows Updates inside the VM itself as they're an integral part of ensuring that VSS runs successfully inside the VM.
   
   

8. If all of the above checks out, the next step is to take a look at the Windows Application event log of the VM itself. Essentially, the VSS process inside the VM (using the actual Exchange/SQL VSS writers) should indeed commit/truncate the logs if behaving properly. By looking at the same time of the backup, you should be able to find relevant events that point to the reason why the logs are not being truncated.