Extra command-line parameters for compression command
By default, Virtualmin runs the gzip or bzip2 commands for compressing backups with no additional parameters. This means that the default compression level and format will be used. However, you can use this field to enter additional parameters, such as --fast to make your backups run faster (at the cost of requiring more space), --best to get better compression (at the cost of CPU time), or --rsyncable to make the file more easily replicatable.