Scenario: I am a new admin for my company and have a single volume of 30TB (28 used) that currently has no backup configured (must be why I have this job). I am looking to at DR/offsite backup opportunities and the several backup companies I have contacted have asked me to first determine my change data rate.

Question: How do I determine my change data rate (files that have changed since last backup) easily?

Notes: I have been told that Beyond Compare and Tree Size Pro can do this but from my research, it appears as if this is not a correct statement. Tree Size Pro support also confirmed that they do not have the ability to track change data.

  • Hardware: Dell PowerVault NX3200
  • Software: Windows Server Storage 2012
  • Storage: 30TB volume

Thank you!


Implement any local backup solution and see how big the deltas are.

Find all files last modified in the past day or so. Sum their sizes. May not be accurate if only some blocks changed, but a simplistic worst case.

  • That's part of the problem. I am trying to determine to change data to help in choosing the correct backup solution. – Mike66350216 Nov 2 '16 at 20:36
  • Then make a guess based on other data, this likely does not need to be precise. Do files frequently get modified? If not, the growth rate by itself rounded up is a decent change rate. Is this small documents and images where most of the file is probably written, or large databases and VM images with their own write patterns? – John Mahowald Nov 4 '16 at 9:52
  • My question was to see if there were options out there that would prevent the need to guess what the change data was. – Mike66350216 Nov 9 '16 at 16:02

Try a "fake" local backup with Robocopy, using the /create flag so that files are created with zero length (empty) in the destination. This gets you away from the problem of not having enough space for a true backup, but still creates a copy of the file metadata you need to track changes. You could even use a small local mounted vhdx as the destination so you can easily discard it afterward. Robocopy should give you a summary of the amount of data that changed from one script run to the next. The numbers may not be extremely accurate, but it could give you a ballpark for how much change data you're dealing with.

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