I often get asked how data compression works in Backup Exec…which one has a better compression ratio, which one is faster etc. Well here’s what I know…
There are 2 data compression types in Backup Exec: Software & Hardware.
- Software Compression basically uses STAC (Storage Allocation and Coding) Program and compresses data before it’s copied to the media drive. STAC was created to compress data at a ratio of 4:1 but certain factors during backups prevent this from happening.
- Hardware Compression Option 1 backs up the data uncompressed then runs an NT compression program on the data whilst on the backup media. This type solely uses the NT hardware compression technology.
- Hardware Compression Option 2 also backs up the data uncompressed but offers 2 options for compression depending on the machine. If NT hardware compression exists, then it uses that by default, else it falls over to STAC compression.
We very seldom see the full compression capacity being used in backups simply coz of the different file types and how they behave when compressed. A .zip file cannot be compressed as it is already in compressed form and the marker is set to 1 (meaning Compression=True). document files like .doc or .docx, .txt etc usually get the full compression capacity (4:1 for STAC, & 2:1 for NT Compression). All in all, it’s rather hard to experience the full compression capacity when running backups in an office environment.
