SD(4)

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/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.