The EZ-Backup software has both client and server level compression options. At Cornell, we force compression ON at the server. We do this to conserve network bandwidth and server storage utilization. 

By using server-level compression, the data that you back up or archive is first compressed by your workstation before being stored on the EZ-Backup server. Compression efficiency depends quite a bit on the type of data that is being compressed. Executables may be less compressible than documents. (Note that the ADSM Scheduler does report the compression percentage in the summary statistics at the end of the scheduler log.) In general, we tend to see about a 2-1 ratio between what is stored on the workstation and what is stored on our EZ-Backup server.

Related notes:

• Files that are compressed on the workstation tend to expand when the EZ-Backup software tries to compress them. The software is smart enough to know not to try compressing them. Instead, the client (workstation) just sends the file as is to the EZ-Backup server.
• It is possible to "exclude" certain files from being backed up at all. 
• As files are changed, extra versioned backup copies of those files are kept around for a time. Defaults: up to two extra copies for up to 30 days. This adds a small amount of extra backup storage, depending on how much data is changed on a daily basis. Rule of thumb: add 5-10%.