How to perform a test to verify if compression is working.

Problem

How to perform a test to verify if compression is working.

Solution

1. Run the following command: (fsutil file createnew testfile.txt 2100000000)
 
Figure 1:
  • This creates a file called testfile.txt and around 2gb size, with content that consists of zeroes.
  • So this file will be highly compressible.
  • This is the minimum file size to get any compression information.
2. Create a new job to backup only this file and compression enabled.
3. Target the backup job to use an overwritable / scratch media.
4. Run the test job.
5. Once the job is completed, check the "compression ratio" for the media used by right click on it and selecting "Properties" under "Devices" tab.
 
Figure 2:

 
6. In figure 2, the compression ratio is 1:1, meaning that there's no compression.
7. If the test shows a higher compression ratio, such as 1.5:1; 2:1 or more,  this means that compression is being enabled and used for the device.
 
NOTE: If software compression is used in a backup job and if the device is a Tape, the data would be precompressed, hence the Tape will show compression ratio as 1:1
 
The compression depends on the type of data that's being backed up and not on the tape itself; ZIP files by instance, are already compressed.
Keep in mind that software compression is the only compression method available for Backup-to-Disk (B2D) jobs due to the obvious lack of media hardware.
See related technotes for more information. 

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