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) |
NOTES:
- Sony SDX-300C is used in the Unylogix UNA-90
- 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,
|