If you want a parallel backup with software compression on local or remote tape devices, <n> copy processes are generally started in parallel, where <n> is normally the number of defined backup devices which are connected. In order to be able to use this parallel copy effectively also for the compression, you should define in directory compress_dir as many directories as there are copy processes. See also exec_parallel.

If you check the readability and completeness of the backup using -w|-verify, the files are restored back to the directories defined in compress_dir . In order to carry out this process in parallel as effectively as possible, you should define as many directories as there are copy processes (the number of copy processes generally corresponds to the number of connected tape devices, see exec_parallel).