Hi aceinc
Welcome to VMTN,
You have an interesting use case,
We have two separate layers
A-VMFS(VMDK)
B-IOPS within Guest OS
For knowing delta in VMDK we obviously have CBT.
For Application IO tracking from within OS you may need to resort to performance monitoring tools to track the process/application that cause the IOPS to files.
But there will be a significant load on a system going this route.
Alternatively you can also consider using utilities like treesize to track the delta filesize and then predict the application that wrote to the files, for instance it should be easy to figure out that a DB write to database files/growth.