Some 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")
HP DDS-2	C1533A	DCLZ (ECMA standard #115)

NOTES:

1. Sony SDX-300C is used in the Avax AMA-50000

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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%
HP DDS-2	DCLZ	2.5:1	2.29:1	91.66%

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Projected Capacity and Throughput

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

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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,
contact Avax first!

For more information, download our white paper in Adobe Acrobat® format, which compares Sony AIT, and DLT technologies.

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