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gordonwd

Typical compression ratio

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What is a "typical" overall compression ratio when using Retrospect Express? A while back, a lot of products seemed to assume at least 2:1 compression (such a when they sell you a 4Gb tape but rate it as holding 8Gb compressed!). However, many of the larger files on people's hard disks these days are already in a compressed format and can't be shrunk much farther. For example, MP3, JPEG, GIF, MPEG, and ZIP files are already compressed, as well as many of .EXE files that are self-installing products or product updates. My latest backups with Backup Express to tape end up at about 1.5:1 compression.

 

 

 

Just wondering.

 

 

 

Doug Gordon

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It depends on the files I guess. I have an Oracle Database on my laptop, and those files are not compressed at all (and in fact are mostly empty). I get 80-90% compression on those files, so 1Gb shrinks to 100-200Mb in the backup. For other file types the compression is pretty low, such as for MP3's etc.

 

 

 

Paul

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For my initial backup Retrospect reports 0% compression, which I find hard to completely believe, but maybe.

 

 

 

Backups since have ranged from 20% to 60%, probably averaging closer to 50%. This is for mainly "business" type data -- not too many jpgs, mp3s, or movies, though with a number a zips and compressed exes.

 

 

 

Ian

 

...

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It is 2:1 for files that can be compressed. Many files cannot be compressed or do not compress very well. www.dantz.com/knowledgebase has an article on compression.

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