When backing up to tape, which is the preferred method of compression?Which is the faster mode of compression?
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 incompatibilitiessecond: 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.
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 problemsThe 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
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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 formatspretty slim delta, when you total it all up.
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.NOTE : If we do not receive your reply within two business days, this post would be marked assumed answered and would be moved to answered questions pool.