Hi managers :
More explanations about my disklabel & show device problem I got
from Peter Stern and Chris Ruhnke :
Peter Stern says a good answert :
You got a fast answer, but it is the wrong answer. disklabel reports
the size in 512 byte blocks and 17824700*512=9.13e+9. Disk
manufacturers report their disk sizes in bytes and not in multiples of
Kbytes (1024 bytes) as do memory manufacturers. It is just a different
and slightly arbitrary definition of Gigabytes which looks better
(as in more is better). This is an old story dating back to the 10MB
and more PC disks.
By the way, formatting a disk and putting on a file system does take
some overhead, but you will only see that when you run the df command
and not from disklabel. In fact, the 9.1GB SHOULD be the formatted
capacity.
Chris Ruhnke specified in the same way :
In defference to Sakellaris Alexander, a better explanation of the
situation is that the 9.1 Gb specification is "raw" capacity -- how many
physical bytes of data can be recorded on the magnetic surface. When a
drive is "formatted" the process records information defining a sector's
location, its size, checksum information, beginning-of-data marks,
end-of-data marks and other such "overhead". Then when the disklabel is
written, the OS and drive take their 2 cents worth; albeit not too much.
Thus a disk that is prepared to receive actual data to be recorded has
already been reduced by as much as 1 to 2 percent by the "overhead"
required to be able to record user data.
Vendors are wont to tout their wares with the biggest numbers they can, so
when you see figures like "9.1 Gb" don't expect to be able to record
9.1 (1024 * 1024 * 1024) user data bytes on the drive. It'll always be
lower!
Many Thanks to Peter and Chris
JEAN
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Received on Fri Nov 20 1998 - 14:20:10 NZDT