My book stidio unused part(could not unmount the disc)


i have an extenal wd my book studio for mac.i’ve connected it with an imac via day after a failed backup with time machine(cause a blackout) i tried to reformat the external but there’s a part (350 gb) used but invisible.when i try to erase the drive this part remains.and also appears in the time machine options(as an excluded part of the disc).lately when i try to erase from the disc utility it appears ‘‘could not un ount the disc’’ you can see a snapshot from the disc utility below…

Screen shot 2011-05-05 at 10.05.49 μ.μ..png

Power outages are common causes for data corruption, Try turning the computer off / disconnect the drive / boot the computer back / re-connect the drive / try click on repair on the FirstAid, you might need to reformat the drive if you are unable to repair it, try click here to view the instructions to repartition the disk, If you have data on the drive that you would like to retrieve, I recommend you to try Mini Tool Data Recovery.

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hello   MR_MKS_Montana.

first of all thanks for the  reply and for the time you spent on my problem.i did the reformat,verify and repair and everything seems to be ok.but  as you can see form the snapshot below  there are 998 gb available but 663 used.what’s happening??? Screen shot 2011-05-06 at 9.43.08 μ.μ..png