[comp.sys.sgi] missing disc space

lacomb@SIERRA.STANFORD.EDU ("Lloyd J. Lacomb") (08/23/88)

Now that the debug partition seems to be well understood, I am still puzzled
by the missing space on the disc.  I have a 380 Mb disc, and when I do a df
I get the following:

Filesystem                  Type kbytes    use  avail %use  Mounted on
/dev/root                   efs   15591   9504   6087  61%  /
/debug                      dbg   58196   5508  52688   9%  /debug
/dev/usr                    efs  236529 132029 104500  56%  /usr
-----------------------------------------------------------------------
TOTAL                            310316

My question is if df reports only 310 Mb including the swap space what
happened to the 70 Mb (plus or minus the 8 Mb of core memory) that my disc 
is supposed to have.  I know that df does not count correctly and that 
a 380 Mb disc does not really have 380 Mb(what a racket!!!) but it
still seems that I'm missing a lot of Mb.  I used to think that most 
of the missing Mb was occupied by the swap space but that appears not to be 
the case.  Can anyone clear this up.


					Thanks,
					Lloyd LaComb
					lacomb@sierra.stanford.edu

olson@anchor.SGI.COM (Dave Olson) (08/23/88)

In article <8808221920.aa01270@SMOKE.BRL.MIL>, lacomb@SIERRA.STANFORD.EDU ("Lloyd J. Lacomb") writes:
>---
> Filesystem                  Type kbytes    use  avail %use  Mounted on
> /dev/root                   efs   15591   9504   6087  61%  /
> /debug                      dbg   58196   5508  52688   9%  /debug
> /dev/usr                    efs  236529 132029 104500  56%  /usr
> TOTAL                            310316
> 
> My question is if df reports only 310 Mb including the swap space what
> happened to the 70 Mb (plus or minus the 8 Mb of core memory) that my disc 
> is supposed to have.
First of all, the size of /debug has NOTHING to do with the amount of
swap space you have.  If your disk is laid out more or less typically
you probably have about 100,000 sectors of swap.  You can find out
using 'swap -l'.  Depending on whether the disk is a SCSI or ESDI
disk, you may have cylinders allocated for forwarding badblocks.
There is also typically about 2200 sectors allocated for the
volume header.  You can use the prtvtoc command to find out
exactly how your disk is laid out.

Assuming you have typical swap and rounding, we get
15600+236500+1100+50000 = 303,200 K bytes.  You don't say what
type of drive it is, but CDC for example, counts Mbytes as 10^6,
not 2^20, and the CDC Wren IV 380 typically formats to about
344 * 10^6 bytes == 328 * 2^20 bytes.  Add in the overhead of
the filesystem for inodes, etc. and you are probably pretty
close.

	Dave Olson, SGI

olson@anchor.SGI.COM (Dave Olson) (08/23/88)

Sorry, I was a little too emphatic in my earlier posting, and the
article got out before I could cancel it (yet another reason
for not posting at the end of a long day)...

The df for the /debug file system DOES have something to with
the amount of swap space you have, it just isn't as reliable
as swap -l or looking at the partition table when trying to
figure out your disk layout..

	Dave Olson, SGI