NETAPP Disk Size

It depends on what you mean by the "actual available space" on the drive. First, you have to know the exact manufacturer's specs for the particular hard disk drive (HDD) you are examining. Part of the problem comes from our translation of a decimal number (250GB - since we like to count in multiples of our fingers and toes) to binary (which is all that our computers REALLY are working with). Go back to simple conversion: 2^10 = 1024 bytes, but computer geeks for a long time have been "rounding" it to 1kB. They know what they mean, but everyone else is confused. This situation gets even more complicated when we get in the billions of bytes of modern multi-GB and now tera-byte HDDs.

Compounding that is the fact that the HDD can have multiple platters, each of which has some binary multiple of bytes on it. A HDD could be all one platter, or have more than one ganged together on one spindle.

As to why your 250GB has only 207.01GB of physical space, the 250GB is only a rounded decimal number approximating the order of magnitude of the actual bytes on the drive. Different 250GB drives from different manufacturers (or different models & configurations even from the same mfr) can have the same 250GB designation, but different actual # of bytes.

Some of the space will be used up by the indexing and addressing system needed to define the working areas of the drive. That's is not available for you to use, but is needed so the data you want can be located in all those buckets of bits.

Also, some of the space is used up by spare sectors, so that defective areas of the drive (and trust me - there are some there!) are "mapped" out by the firmware and spare areas mapped in their place. The error detection and correction is able to swap out these bad sectors so that you don't even know you have them there.

Ultimately, you get somewhere close to the 250GB on the label, but an exact number probably is beyond the ability of the average user to determine.