Have you ever wanted a way to know how many files, on average, change on your network per day? This is crucial to estimating how large your nightly incremental backup will be. We first provided a way to do this in our blog post 6 Easy Steps to Calculate Data Changed Per Day for Backup. We wanted to provide a more automated, scripted way to estimate this calculation, so Highly Reliable Systems wrote the Incremental Backup Calculator.


Since the High-Rely Incremental Backup Calculator uses Cscript, simply open a Command Prompt window and use the general form Cscript bsize.vbs J: 10/01/2013 10/31/2013  where you will change J: to your network drive letter or path and the dates to match a range you want to scan for modified files. The program automatically skips system files such as hiberfil.sys and pagefil.sys that can be quite large and really throw your results off. As mentioned in the blog post above, this should be a “worst case” estimation, because it reflects total file sizes rather than modified blocks, but it should help you get an idea how big your changes will be.A Better BDR: Back-up to 18TB RAIDPacs

Don’t forget to divide the total size returned by the number of days you scanned to get an average per day. You could skip weekends if you want to analyze only weekdays by providing the script week day ranges.

If you add /Verbose the command will list the folders as it scans and show you which files matched. Use the typical trick of using a greater than symbol at the end of the command line to redirect screen output to a text file if you want to create a log of the results. If you do this nothing will display on the screen so be patient for it to finish. The text file can be useful with a document editor or use Wordpad to search for certain files after the script finishes.  Example:

Cscript bsize.vbs /verbose J: 10/01/2013 10/31/2013 >logfile.txt

Ctrl-C will abort the script if you grow impatient. We’ve provided a download button to the script here.  Enjoy, and tell your friends about High-Rely!

Download: High-Rely Incremental Backup Calculator