Portable Hard Drive for iMac Question

in General Discussion edited January 2014
I purchase a WD 640G harddrive for my iMac G5, but when install to my Mac, I can see only have 598G available, which mean I lost 42G. Did this sound correct? Is when you install new hard drive, there are some space will automatic lost by the configuartion or? Any advice for this new hard drive install into iMac computer?


  • Reply 1 of 2
    Yes, you will loose some space to the file system. The drive sets aside a certain amount of it's space for keeping track of the files you put on it.

    42 GB is a bit much though... but every WD HDD I've purchased also had some useless (to me) software on the drive... that could be taking up some of that room... (things like backup programs, anti-virus trials, etc.)
  • Reply 2 of 2
    mr. hmr. h Posts: 4,819member
    This is all down to the difference between base 10 and base 2 sizes.

    Your HDD is a 640 Gigabyte hard drive. The prefix "Giga" means 10^9 aka 1 billion aka 1,000,000,000. So your hard-drive can store approx. 640,000,000,000 bytes.

    Computers use base two numbers, and when they say GB, they really mean GiB, i.e. Gibibyte. The prefix "Gibi" means 2^30, which is 1,073,741,824. In other words, a gigabyte and a gibibyte are not the same thing.

    Knowing that your HDD can store approx 640,000,000,000 bytes, how many GiB does that work out as? The answer is 640,000,000,000/1,073,741,824, which is 596.

    Your HDD is being reported as having 598 GiB available, so you actually got a slightly bigger hard drive than you thought.
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