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
<
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/sd
up-
block mode
SCSI
disk unit
u,
partition
p
/dev/rsd
up-
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.