16791: Archive Compression in Acronis Products

Acronis products save backup data in the proprietary TIB format using compression that reduces the amount of storage space needed for backups. Compression is used both in Windows and Linux operating systems and in Acronis Bootable Media.

Effective data compression level and resulting archive size depends on the type of files stored in the backup: even maximum compression cannot significantly reduce the backup size if the backup contains already compressed files, like .jpg, .pdf or .mp3. However, formats such as .doc or .xls will be compressed well.


You can choose the compression level for a backup in Backup options. For most products, the compression levels are:

  • None - the data is copied without any compression, which may significantly increase the backup file size (especially with sector-by-sector backup);
  • Normal - the recommended data compression level (set by default);
  • High - higher backup file compression level, takes more time to create a backup;
  • Maximum - maximum backup compression, but takes a long time to create a backup.

Acronis products use two libraries for compression: zlib and Acronis compression algorithm. Both libraries provide approximately the same ratios of compression.

Backup type Compression library used
Disk and partition backup: Normal compression rate Acronis compression algorithm
Disk and partition backup: other compression rates zlib
File and folder backup zlib

Zlib is a third-party compression library. See Third Party Software Used in Acronis Products.

Compression ratio example

Example of compression ratio for different compression levels and different data types.

Acronis True Image Home 2011:

Backup archive type Initial data size Compression level
None Normal High Max
Disk image 3.88 GB = System + 1 GB of MP3 files 3.88 GB (100%) 2.82 GB (72.7%) 2.71 GB (69.9%)  2.68 GB (69.1%)
Disk image  3.88 GB = System + 1 GB of DOC and XLS files 3.88 GB (100%) 2.47 GB (63.7%) 2.34 GB (60.3%) 2.31 GB (59.5%)


Acronis Backup & Recovery 10, Acronis Snap Deploy 3:

Backup archive type Initial data size Compression level
None Normal High Max
Disk image 13.78 GB 13.78 GB (100%) 10.11 GB (73,3%) 9.83 GB (71.4%) 9.77 GB (70.9%)
File backup 13.75 GB 13.75 GB (100%) 9.63 GB (70%) 9.59 GB (69.8%) 9.52 GB (69.3%)


(!) Actual ratio of compression depends on data type and may be different on your system.



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