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No Compression

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Just installed Retrospect on our network. The first backup (backup server) worked peachy kean. Well almost.




The servers own C: drive came up with 0% compression. All other clients had varying degrees of compression (from 9 to 37%).




Why did the c: drive have no compression? What am I doing. Wrong?







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Retrospect optionally uses either software compression or hardware compression, depending upon the device you are backing up to.




Hardware compression: Currently the only devices Retrospect supports for backup that use hardware compression are tape drives. You choose to enable or disable hardware compression on a set by set basis, when you create the backup set (there is a checkbox, default on, that tells Retrospect to use hardware compression if it is available). If your device does not support hardware compression, leaving the checkbox set does no harm. If you choose to encrypt your backup set, Retrospect disables hardware compression, as encrypted data does not compress well.




Software compression: You can tell Retrospect to compress data while backing up to any device using Retrospect's software data compression. This may make the backup take a bit longer, but typically saves substantial space. If you are using a backup device that supports hardware compression, Retrospect lets the device compress the data, as this is faster. If you enable compression and encryption in Retrospect, Retrospect first compresses the data, and then encrypts it.




Retrospect compresses files into its own proprietary format using a "lossless" compression process. This means that Retrospect compresses your data in such a way that all original bytes of your source data are preserved. This is similar in concept to the popular compression utilities PKZIP (Windows) and StuffIt (Macintosh), which compress and decompress preserving the original data byte for byte. If you back up a file using Retrospect's software data compression, and then you restore that file, you get back every byte, exactly as it was when you performed the backup.




In contrast, some compression methods such as MPEG, compress files using a "lossy" compression algorithm, which actually discards some content in favor of a smaller file. For obvious reasons, lossy algorithms aren't appropriate for backup applications, but work fine for many audio or video applications. Retrospect does not use these compression methods.





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Thanks Melissa, I appreciate the reply. I am aware, though, of all of the above. My question is why does one drive (the c: drive in this case) have no compression at all while all of the other drives (clients on a network) have compression. The backup was run from one script (backup server).




The drive in question (C:) contains primarily MS Word, Excel, and other text based documents that should show a fair amount of compression (as compared to zip and other files that do not compress well.)




The 'compress flag', as far as I can tell, is set in one location/dialog box and affects all of the backup and not just one drive/client in particular.




We're not doing encryption. We just want to compress.




Thanks :-) !





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