What is the capacity of a BD-R disk really?

Andre Robatino robatino at fedoraproject.org
Sat Nov 26 15:15:29 UTC 2011

Tom Horsley <horsley1953 <at> gmail.com> writes:

> So, does anyone have any pointers to information on the
> actual capacity of BD-R disks? None of the tools on fedora
> seem to agree, and none of them appear to be correct
> either . (And web searches are remarkably fruitless
> on this topic).
> Is BD-R back to the days where you have to do a simulated
> write before you can get an actual answer? Or is it simpler
> just to provide about 3GB of slop to be sure everything fits?

The capacity of all optical media with the exception of CDs are measured using
SI units (see https://en.wikipedia.org/wiki/Binary_prefixes#Optical_discs ), so
if the container says "25 GB", that means 25*1000^3 bytes (NOT 25*1024^3). The
capacity of a "700 MB" CD is actually 700 MiB = 700*1024^2 bytes. You should
check whether when k3b says "GB", it really means that (1000^3 bytes), or if
it's actually referring to GiB (1024^3 bytes).

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