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software vs. hardware compression

Created: 10 Nov 2005 • Updated: 21 May 2010 | 4 comments

When backing up to tape, which is the preferred method of compression?
Which is the faster mode of compression?

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Thomas Bianco's picture

hardware is always preferred over software, for 2 reasons.

first: hardware compression is well tested with your tape drive, and there is never any fear of incompatibilities

second: hardware compression is MUCH faster then software. most hardware compression is wire speed, meaning it can happen as fast or faster then the tape can accept data, where as software compression has to be processed by the CPU.

Ken Putnam's picture

In my experience with modern systems, you see very little if any difference in throughput between HW and SW compression. Back in the 286/386/486 days this was indeed a problem.

As for no incompatibilities with HW - that may be true now or if you never plan to add new drives or replace the existing drive(s), but I got almost got burned several years ago trying to restore tapes made on a DLT4000 w/HW compression on a DLT7000. BE would tell me the tape was unreadable. Luckily I still had the DLT4000 available. Since then I've stayed with SW, and had absolutely no problems

The one major caveat with SW compression is that you MUST use the same product to restore that was used to Backup. IE NTBackup or ArcServe will not read tapes written by BE with SW compression

If this response answers your concern, please mark it as a "solution"

Thomas Bianco's picture

well Wayne- seems you have an interesting conundrum.

hardware compression all happens outside the main cpu, which admittedly will have nothing better to do with it's time when backing stuff up.

software compression locks you into a specific product, but not a specific tape drive, where has hardware compression may require the same tape drive, but will require the same backup software software due to differing tape formats

pretty slim delta, when you total it all up.

Deepali Badave's picture

Hello,

The Backup Exec includes two data compression types.
Software Compression and Hardware Compression.
The compression type is available under Tools >> Options >> Backup >>
Compression Type in the Backup Exec.
1) Software - Select this option to use STAC(TM) software data compression,
which compresses the data before it is sent to the storage device.
2) a) Hardware - Select this option to use
hardware data compression (if the storage device supports it). If the drive
does not feature data compression the data is backed up uncompressed.
b) Hardware - Select this option to use
hardware data compression (if the storage device supports it). If the drive
does not feature hardware data compression, STAC software compression is
used.
Please note: -
when using compression it is important to remember that the 2:1 compression
ratio frequently assumed or stated in technical documentation is an ideal
seldom reached as a practical average. Some files compress better than
others. Text files are probably the most compressible files in general
while high density graphics files like files with .jpg, .gif, .zip, or .cab
extensions are not likely to compress at all. Also, many programs,
including some database and mail programs, already compress the files they
control.


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