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Retrospect Compression = 1.5x size INCREASE? (note: sparse files supported)


SeanSeanSean

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Hi,

 

I am trying to backup some virtual disk files. The virtual disk files are in TrueCrypt (.tc) format. However, compression appears to make the files 50% larger! What is going on? Is this a bug?

 

The files are stored as NTFS sparse files with Retrospect Professional Windows 7.5.324 / driver hotfix 5.9.102. Retrospect handles the sparse files as it should: only the nonsparse data is backed up. However, that is not the point of my inquiry. However, if you look at the file sizes, you can see that there is a consistent 50% increase for Retrospect-compressed files, so the nonsparse virtual disk file occupies an extra 60 MB of space!

 

filename | Size

1 nocompression.rbf | 4,898 KB

2 withcompression.rbf | 6,732 KB

3 nocompression.rbf | 4,899 KB

4 withcompression.rbf | 6,732 KB

5 (regular) nocompression.rbf | 122,949 KB

6 (regular) withcompression.rbf | 180,816 KB

 

 

filename | Size | Size on Disk

volume as 4.75mb sparse file.tc | 122,880 KB | 4.75 MB (4,980,736 bytes)

volume as 120mb regular file.tc | 122,880 KB | 120 MB (125,829,120 bytes)

 

All sizes are as reported by Windows Explorer on Windows XP SP2. This is Retrospect Pro Win 7.5.324 / 7.5.9.102.

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