Where Did All The Bytes Go?
Dinah McNutt
Tivoli Systems
Michael Pearlman
Rice University
Abstract
Configuring, installing, re-configuring, and re-installing disk drives
can be time consuming. Understanding the physical disk and how UNIX
file systems are laid out on disk drives can not only help an
administrator troubleshoot problems, but can allow him/her to maximize
the amount of disk space available. Standard formatting utilities tend
to configure disks with similar geometry identically. By using
different geometry parameters or third party formatting programs, you
can get the maximum amount of disk space from your drives. This paper
is a tutorial on understanding SCSI disk drive geometry (and how it
differs from more traditional drives ) and the steps required to get a
disk drive to the point where it is usable (e.g., with a UNIX file
system on it.) It includes practical tips such as questions to ask
vendors so you know how much usable space you will have when you
purchase a disk drive. It also include a case study where we show how
you can squeeze additional usable disk space from a drive. This paper
is targeted at novice system administrators, but experienced
administrators who want to learn more about disk drives will hopefully
learn something from reading this paper. The examples we use will be
based on a BSD system, but the concepts apply to other types of UNIX
systems as well.
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