36.4GB drive formats out to 32.8GB? what am I missing please
jerrymc at clunix.cl.msu.edu
Sun Jun 12 16:12:30 GMT 2005
> > I have always seen drives format out at less but the thing that threw me was
> > that 36.4 was listed as "formatted capacity" - by IBM (not Seagate). This
> > helps though. Somehow this reminds me of the # of hotdogs in a pack vs. # of
> > buns.
> todays drives are always factory formatted and it's always "formatted
> capacity". in microsoft world "formatting" and "making filesystem" is
> commonly referred as one job which is total nonsense.
"Formatting" is not the same as building a filesystem on the drive.
So, after it is "formatted" at the factory, it is still necessary to
make slices and divide the slices in to partitions and newfs the partitions
to make file systems. SOme people use a generic work format to mean
those things. It is not quite accurate, but that is what was meant.
In addition to that filesystem building, manufacturer's "formatted" capacity
is given in decimal so a Gigabyte is 1,000,000,000 bytes whereas system
utilities use the power of two numbering for giga which is 2^30
or 1,073,741,824 so there will be less GigaBytes.
Then the system, by default reserves 8% of the filesystem for system overfill.
So, those will completely account for differences.
> >> 2) formatting itself takes some space for superblocks etc
> > Figured, but not much, right?
> >> 3) some psace is reserved (man newfs and tunefs for info)
> > Read those man pages and that helped a lot. I have read this before and it
> > wasn't retained. 8% is the kind of loss I was looking for.
> > Thanks for all the quick answers.
> > d.
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