Advantages of using software compression over hardware compression with Amanda

There are multiple reasons to use software compression over hardware compression with Amanda:

• Amanda allows users to selectively choose DLEs which compression algorithm to use, whether to use compression or not for a DLE. For example: Compressing video or image files will be counter productive.
• Amanda allows compression to be done either on the client or on the server. If the backup data is compressed on the client, the backup window will be smaller as there is lesser data has to be transferred to the server.
• Amanda scheduling and media utilization works better when the media capacity numbers are accurate. Amanda makes estimates how big the backups will be (level 0, level N, and level N+1 where N is the last level of backup). Backup size estimates along with the media capacity value (length) provided in the tapetype definition in the amanda.conf is used to decide the backup plan. When the tape drive does not do any compression, the tape capacity value can be pretty accurate. When doing hardware compression with the tape drive, user will have to guess how much the data will compress because it will depend on data.