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Why do I get only 4.5 GB out of a 5 GB Exabyte 8 mm tape?

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I use Retrospect 6.0 for Windows Professional. My question concerns the amount of "overhead" that Retrospect uses on a backup job.


Ive been backing up to tape a LOT of zip files, mp3s, etc., and other files that can't be compressed further. My drive is an Exabyte 8720 (internal version) on SCSI-160. No problems there.


Doing all these backups, I consistently get only 4.4 - 4.6 GB of files on one 112m tape. Never 4.9 or 5.0. If I use a 160 m tape, I get about 6.5 - 6.7 GB. This is a local backup, streaming data at 50+ MB/second, so I don't think I'm getting buffer underruns.


What is happening here? confused.gif

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Mayoff said:

Please see the media capacity FAQ




Thanks. I've gone through the FAQ, but that doesn't tell me why Retrospect identifies at 112 m Exa tape as 4.3 GB, when the rated capacity is 5.0 GB. Is this based on my historical usage, or does this include a "fudge factor" smile.gif to account for lost capacity?


Also, is there a lot of overhead for each file stored on tape, in effect a file "header" or "trailer."


philx509 cool.gif

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