NAME
sd —
SCSI and ATAPI disk driver
SYNOPSIS
sd* at scsibus? target ? lun ?
sd3 at scsibus0 target 3 lun 0
sd* at atapibus? drive ? flags 0x0000
DESCRIPTION
The
sd driver provides support for SCSI bus and Advanced
Technology Attachment Packet Interface (ATAPI) disks. It allows the disk to be
divided up into a set of pseudo devices called
partitions.
In general the interfaces are similar to those described by
wd(4).
Where the
wd(4) device has a fairly
low level interface to the system, SCSI devices have a much higher level
interface and talk to the system via a SCSI host adapter (e.g.,
ahc(4)). A SCSI adapter must also
be separately configured into the system before a SCSI disk can be configured.
When the SCSI adapter is probed during boot, the SCSI bus is scanned for
devices. Any devices found which answer as
‘
Direct’ type devices will be attached to the
sd driver.
For the use of flags with ATAPI devices, see
wd(4).
PARTITIONING
On many systems
disklabel(8) is
used to partition the drive into filesystems. On some systems the
NetBSD portion of the disk resides within a native
partition, and another program is used to create the
NetBSD portion.
For example, the i386 port uses
fdisk(8) to partition the disk
into a BIOS level partition. This allows sharing the disk with other operating
systems.
CONFIGURATION OPTIONS
The following
config(1) options
may be applied to SCSI disks as well as to other disks.
-
-
SDRETRIES
- Set the number of retries that will be performed for
operations it makes sense to retry (e.g., normal reads and writes). The
default is four (4).
-
-
SD_IO_TIMEOUT
- Set amount of time, in milliseconds, a normal read or write
is expected to take. The defaults is sixty seconds (60000 milliseconds).
This is used to set watchdog timers in the SCSI HBA driver to catch
commands that might have died on the device.
IOCTLS
The following
ioctl(2) calls apply
to SCSI disks as well as to other disks. They are defined in the header file
<sys/dkio.h> and use data structures
defined in
<sys/disklabel.h>.
-
-
DIOCGDINFO
- Read, from the kernel, the in-core copy of the disklabel
for the drive. This may be a fictitious disklabel if the drive has never
been initialized, in which case it will contain information read from the
SCSI inquiry commands.
-
-
DIOCSDINFO
- Give the driver a new disklabel to use. The driver
will not write the new disklabel to the disk.
-
-
DIOCKLABEL
- Keep or drop the in-core disklabel on the last close.
-
-
DIOCWLABEL
- Enable or disable the driver's software write protect of
the disklabel on the disk.
-
-
DIOCWDINFO
- Give the driver a new disklabel to use. The driver
will write the new disklabel to the disk.
-
-
DIOCLOCK
- Lock the media cartridge into the device, or unlock a
cartridge previously locked. Used to prevent user and software eject while
the media is in use.
-
-
DIOCEJECT
- Eject the media cartridge from a removable device.
In addition, the
scsi(4) general
ioctl() commands may be used with the
sd
driver, but only against the ‘
c
’ (whole
disk) partition.
NOTES
If a removable device is attached to the
sd driver, then the
act of changing the media will invalidate the disklabel and information held
within the kernel. To avoid corruption, all accesses to the device will be
discarded until there are no more open file descriptors referencing the
device. During this period, all new open attempts will be rejected. When no
more open file descriptors reference the device, the first next open will load
a new set of parameters (including disklabel) for the drive.
FILES
- /dev/sdup
- block mode SCSI disk unit u,
partition p
- /dev/rsdup
- raw mode SCSI disk unit u, partition
p
DIAGNOSTICS
None.
SEE ALSO
ioctl(2),
intro(4),
scsi(4),
wd(4),
disklabel(5),
disklabel(8),
fdisk(8),
scsictl(8)
HISTORY
The
sd driver was originally written for Mach 2.5, and was
ported to
FreeBSD by Julian Elischer. It was later
ported to
NetBSD.