NAME

cmdk - common disk driver

AVAILABILITY

x86

DESCRIPTION

The cmdk device driver is a common interface to various disk devices. The driver supports magnetic fixed disks, magnetic removable disks, and both 512-byte and 2K-byte CD-ROM drives.

The block-files access the disk using the system's normal buffering mechanism and are read and written without regard to physical disk records. There is also a "raw" interface that provides for direct transmission between the disk and the user's read or write buffer. A single read or write call usually results in one I/O operation; raw I/O is therefore considerably more efficient when many bytes are transmitted. The names of the block files are found in /dev/dsk; the names of the raw files are found in /dev/rdsk.

I/O requests to the magnetic disk must have an offset and transfer length that is a multiple of 512 bytes or the driver returns an EINVAL error. However, I/O requests to the 2K-byte CD-ROM drive must be a multiple of 2K bytes. Otherwise, the driver returns an EINVAL error, too.

Slice 0 is normally used for the root file system on a disk, slice 1 as a paging area (for example, swap), and slice 2 for backing up the entire Solaris fdisk partition. Other slices may be used for usr file systems or system reserved area.

Fdisk partition 0 is to access the entire disk and is generally used by the fdisk(1M) program.

FILES

/dev/dsk/cntndn[s|p]n

block device

/dev/rdsk/cntndn[s|p]n

raw device

where:

cn

controller n

tn

target id n (0-6)

dn

lun n (0-7)

sn

UNIX system slice n (0-15)

pn

fdisk partition (0)

SEE ALSO

fdisk(1M), mount (1M),lseek(2), read (2),write(2), directory(3C), vfstab(4), dkio(7)