Never use this product! I tried to resize a non-boot volume from 76 GB down to 67 GB. I repaired the drive before the process with the Disk Utility, until there were no problems, and when i started the volumeworks process, it said: Defragmenting. I went away and came back some hours later. It seemed that everything just went fine! No error message and the new size was here! I was happy with the new 9GB partition, installed YDL and everything seemed fine.
But later I found out, nearly half of the data on the disk is destroyed! Every second file doesn't open anymore or has false content! I guess it has moved some files, without correcting the folder-tree, or whatever it is called. Or it didn't move the data, but changed the "folder-tree". In any case is the result, that the real file position doen't match the file position in the node-tree, folder-tree or whatever it is called. That's a BIG BUG and makes the software crap!
Beware of using it! IT WILL DESTROY YOUR DATA! Make a Backup before trying it out! (then you can use Disk Utility too, so this app makes no sense). It should be called alpha version or something like that and needs a lot of testing and fixing! I read a test and it seemed they had no problems, but maybe they didn't really test the files on the drive! My mistake is a warning for you! Hope this helps someone...