Straight Talk on Data Compression

The following tables give the results of real world testing on 4 different tape drives.

Testing was done using the Calgary/Canterbury compression corpus; a series of text and binary files compiled specifically for testing data compression.

Tape Drives Tested
Drive Model Compression Algorithm
Sony AIT(1) SDX-300C Advanced Lossless Data Compression (ADLC)
Quantum DLT DLT-7000 DLZ (Digital Lempel Ziv - STAC "Platinum chip")
Exabyte Mammoth (2) EXB-8900 IDRC
HP DDS-2 C1533A DCLZ (ECMA standard #115)


  1. Sony SDX-300C is used in the Unylogix UNA-90
  2. Exabyte Mammoth(EXB-8900) is used in the Unylogix UNM-40

Comparison of Manufacturers
vs Tested Compression Ratios
Drive Algorithm Rated Compression Tested Compression % of Rating
Sony AIT ALDC 2.6:1 2.55:1 97.97%
DLT-7000 DLZ 2.0:1 1.81:1 90.43%
Mammoth IDRC 2.0:1 1.82:1 91.00%
HP DDS-2 DCLZ 2.5:1 2.29:1 91.66%

Projected Capacity and Throughput
  Sony AIT DLT-7000 Mammoth DDS-2
Native Capacity(GB) 25.0 35.0 20.0 4.0
Projected Compressed Capacity 63.7 63.3 36.4 9.2
Native Throughput (MB/sec) 3.0 5.0 3.0 0.5
Projected Compressed Throughput(MB/sec) 7.6 9.0 5.5 1.1

And the winner is.......

From the above tables, the clear winner is IBM's ADLC algorithm which, in the drives tested, is only used in the Sony SDX-300C.

Interestingly, based on the testing data, the SDX-300C provides better capacity, and only slightly slower data transfer rates, than the DLT-7000. This in a drive which costs LESS than a DLT-4000.

But remember, whatever your backup requirements,