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Retrospect uses compression only when it wants to


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I'm backing up to internal hard disks and for each script have selected the option "Data Compression in Software". When I look at the Operations Log, sometimes Retrospect will use compression for a source, sometimes it shows 0% compression. There is no hardware compression set on the hard disks. Retrospect 6.5 on XP Home.



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  • 3 weeks later...


Scott(BAH) said:



I'm not a Retrospect Expert, but I would assume if you see that message the the files that you backed up were not able to be compressed. Hence the 0% compression. The files could have been graphic files or could have already been compressed (.ZIP,.TAR, etc...)





My experience has been, at least for a Recyle backup, that Retrospect does not do as good a job at compressing as some other programs. THis is based solely on the percentage figures reported by retrospect and calculating the percent done by BackUp MyPC. Recently, I did a recycle backup with REtrospect and full backup wit BUMP to the same USB drive. Retrospect claimed to have a 13% compression. BUMP was, as I recall, 29%. Backups were run within a couple of hours of each other so, in effect, th esame files were backed up in both cases,


However, I do believe that the 0% figure could be misleading, and perhaps, the way Retrospect rounds its numbers could make compression seem worse than it really is.


I would suggest that, instead of using percentages, the number of actual bytes in the files and the resultant number of bytes backed up, after compression, be reported.


It also may be useful to produce, optionally, a separate log of all files backed up, giving their original size and their compressed size.


Perhaps, Retrospect does not compress certain types of files, e.g., PDF, because it is felt that would not be beneficial. I have fould that PDF files can usually be compressed, but not by much. Perhaps, there should be a user option to select which of such types to compress?

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