Re: Partition Problems w/ 810mb HD

[cmcmanis@scndprsn.Eng.Sun.COM (Chuck McManis)]

>...but I'm still curious about the formatting issue...
> 
>I have just checked a huge UNIX file server which we have
>here, which has disks of every size from 200 Meg to 2 Gigabytes.
>All of them show ~ 10% less space available for use than
>their nominal size. DOS may not use quite as much as Unix
>but still... !


My last post too, the answer to your question is that there is
disk formatting, and their is file system formatting and they
are different beasts.

Disk Formatting is the process whereby raw bits are written to
the disk to identify where the sectors are and where the bad
bits are. In DOS land this is called a "low level" format.

File System Formatting is the process whereby the available
bytes of storage are preallocated to "meta data" such as
directories, file pointers, etc, and just "data" which is
contained in the files. 

Inefficient file systems are the bane of DOS and its worst
feature. Basically on every DOS version up to the Windows '95
release the file system wanted to break the file system up into
chunks that it could manage with a simple algorithm. Because
of this, if you have a 540MB disk, and you partition it as one
big disk under DOS, the minimum file size is 16KB because that
is the smallest allocation block that you can use and have the
whole disk representable as a signed 16 bit offset. 

File system efficiency is the ratio of actual data bytes stored
over the used disk allocation space. On DOS that can be 60%. On
UNIX with FFS that can be 72 - 88%, on AmigaDOS it could reach
a pretty impressive 95%. 

--Chuck

P.S. Also UNIX "saves" that last 10% for emergencies. If you're
root you can fill your disks up to being 110% full.