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.