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The cmdk device driver is a common interface to various
disk devices. The driver supports magnetic fixed disks and magnetic removable
disks.
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.
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
fdisk partition for Solaris software. 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.
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