usr/src/share/man/man4/drum.4

.\" Copyright (c) 1980, 1991 Regents of the University of California.
.\" All rights reserved.
.\"
.\" %sccs.include.redist.man%
.\"
.\"     @(#)drum.4      6.2 (Berkeley) %G%
.\"
.Dd
.Dt DRUM 4
.Os BSD 4
.Sh NAME
.Nm drum
.Nd paging device
.Sh DESCRIPTION
This file refers to the paging device in use by the system.
This may actually be a subdevice of one of the disk drivers, but in
a system with paging interleaved across multiple disk drives
it provides an indirect driver for the multiple drives.
.Sh FILES
.Bl -tag -width /dev/drum
.It Pa /dev/drum
.El
.Sh HISTORY
The
.Nm
special file appeared in
.Bx 3.0 .
.Sh BUGS
Reads from the drum are not allowed across the interleaving boundaries.
Since these only occur every .5Mbytes
or so,
and since the system never allocates blocks across the boundary,
this is usually not a problem.