Harddrive size being reported incorrectly?

[Jerry McAllister]

> 
> Hello, 
> 
> I've recently purchased an IDE 320GB Western Digital WD3200JB-22KFA0 
> harddrive for use in my FreeBSD 6.0-RELEASE fileserver. The BIOS in the system 
> reports the drive as being a 320GB, but FreeBSD (dmesg) sees it as a 305245MB 
> (or 298GB drive) in two separate machines. When it has finally been formatted 
> for use, I get 289GB of available space.

A nominal 320GB drive works out to 298.02 GB using the 1024 MB number
system that the system uses.

eg  320,000,000,000 / 1024 / 1024 / 1024 / 1024 = 298.02
or  320,000,000,000 / 1,073,741,824 = 298.02

> Now, I understand that harddrive manufacturers measure things differently 
> (1000kbytes per gbyte rather than 1024, or something like that) than 
> expected, but I've been told by a few people that I should be getting around 
> 305-312GB of available space after the drive has been formatted. 

They didn't do their arithmetic.

When you slice and partition the drive, there will likely be a handful
of sectors that don't round out to an even value so those are dropped.
Then, when you do the newfs, some space is taken by the spare superblocks
and finally the system reserves 8%.     So, I would say you are getting
it all.

> sysinstall had to adjust the drive geometry because the reported one was 
> 'invalid'. I tried to manually specify the geometry BIOS reported, but this 
> too was rejected as invalid. 

Let the system do what it thinks is right.
You are not losing any due to invalid geometry.

> 
> BIOS Geometry-CYL/HD/SECT: 65535/16/255 
> 
> Am I really getting the full potential out of this drive, or is something 
> wrong? 

Doesn't look like anything is wrong.   It looks right.

////jerry

> 
> Thanks,
> -- 
> Travis Poppe
> IRC: tlp @ irc.freenode.net
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