rz(4) Kernel Interfaces Manual rz(4)
Name
rz - SCSI disk interface
Syntax
VAX NCR 5380:
adapter uba0 at nexus?
controller scsi0 at uba0 csr 0x200c0080 vector szintr
disk rz0 at scsi0 drive 0
VAX DEC SII:
adapter ibus0 at nexus?
controller sii0 at ibus? vector sii_intr
disk rz0 at sii0 drive 0
RISC DEC SII:
adapter ibus0 at nexus?
controller sii0 at ibus? vector sii_intr
disk rz0 at sii0 drive 0
RISC DEC KZQ:
adapter uba0 at nexus?
controller kzq0 at ibus? csr 0761300vector sii_intr
disk rz0 at kzq0 drive 0
RISC NCR ASC:
adapter ibus0 at nexus?
controller asc0 at ibus? vector ascintr
disk rz0 at asc0 drive 0
Description
The driver is for all Digital SCSI disk drives.
The following rules are used to determine the major and minor numbers that are associated with an type disk. There is one major number
used to represent disks. The major number represents 32 disks. The minor number is used to represent the both the SCSI unit number and
partition. A disk partition refers to a designated portion of the physical disk. To accomplish this, the 8-bit minor number is broken up
into two parts. The low three bits of the minor number specify a disk partition. These three bits allow for the naming of eight parti-
tions. The partitions have a letter, a through h, as their name. The upper five bits of the minor number specify the SCSI unit number
within a group of 32 disks.
The device special file names associated with disks are based on the following conventions. These conventions are closely associated with
the minor number assigned to the disk. The standard device names begin with for the block special file and for the raw (character) special
file. Following the is the logical unit number and then a letter, a through h, to represent the partition. Throughout this reference
page, the question mark (?) character represents the logical unit number in the name of the device special file. For example, rz?b could
represent rz0b, rz1b, and so on.
The following examples illustrate how the SCSI unit number is calculated given the major and minor number of an disk. For the device spe-
cial file rrz6a, the major number is 56 and the minor number is 48. The partition is represented by the lower three bits of the number 48.
The lower three bits are 0, which specifies the ``a'' partition. The upper five bits of 48 specify the number 6. The major number is 56.
Because 56 is the base major number, it represents the group of 32 disks. Putting all these pieces together reveals that the major/minor
pair 56/48 refers to the ``a'' partition of SCSI unit 6.
The disk can be accessed through either the block special file or the character special file. The block special file accesses the disk
using the file system's normal buffering mechanism. Reads and writes to the block special file can specify any size. This avoids the need
to limit data transfers to the size of physical disk records and to calculate offsets within disk records. The file system can break up
large read and write requests into smaller fixed size transfers to the disk.
The character special file provides a raw interface that allows for direct transmission between the disk and the user's read or write buf-
fer. In contrast to the block special file, reads and writes to the raw interface must be done on full sectors only. For this reason, in
raw I/O, counts must be a multiple of 512 bytes (a disk sector). In the same manner, calls must specify a multiple of 512 bytes. A single
read or write to the raw interface results in exactly one I/O operation. Consequently raw I/O may be considerably more efficient for large
transfers. Multiply buffered I/O operations are possible to any raw SCSI device. (See for more information.)
For systems with SCSI disks, the first boot of the ULTRIX software after the system is powered on may take longer than expected. This delay
is normal and is caused by the software spinning up the SCSI disk drives.
Disk Support
This driver handles all disk drives that can be connected to the SCSI bus. Consult the ULTRIX Software Product Description to determine
which drives are supported for which CPU types and hardware configurations.
The starting location and length (in 512 byte sectors) of the disk partitions of each drive are shown in the following table. Partition
sizes can be changed by For further information, see
RZ22 partitions
disk start length
rz?a 0 32768
rz?b 32768 69664
rz?c 0 102431
rz?d 0 0
rz?e 0 0
rz?f 0 0
rz?g 0 0
rz?h 0 0
RZ23 partitions
disk start length
rz?a 0 32768
rz?b 32768 66690
rz?c 0 204864
rz?d 99458 35135
rz?e 134593 35135
rz?f 169728 35136
rz?g 99458 105406
rz?h 134593 70271
RZ23L partitions
disk start length
rz?a 0 32768
rz?b 32768 66690
rz?c 0 237588
rz?d 99458 35135
rz?e 134593 35135
rz?f 169728 67860
rz?g 99458 138130
rz?h 134593 102995
RZ24 partitions
disk start length
rz?a 0 32768
rz?b 32768 131072
rz?c 0 409792
rz?d 163840 81984
rz?e 245824 81984
rz?f 327808 81984
rz?g 163840 245952
rz?h 0 0
RZ55 partitions
disk start length
rz?a 0 32768
rz?b 32768 131072
rz?c 0 649040
rz?d 163840 152446
rz?e 316286 152446
rz?f 468732 180308
rz?g 163840 485200
rz?h 0 0
RZ56 partitions
disk start length
rz?a 0 32768
rz?b 32768 131072
rz?c 0 1299174
rz?d 163840 292530
rz?e 456370 292530
rz?f 748900 550273
rz?g 163840 1135334
rz?h 731506 567668
RZ57 partitions
disk start length
rz?a 0 32768
rz?b 32768 184320
rz?c 0 2025788
rz?d 831488 299008
rz?e 1130496 299008
rz?f 1429504 596284
rz?g 217088 614400
rz?h 831488 1194300
RRD40/RRD42 (read only) partitions
disk start length
rz?a 0 (size varies per CD)
rz?b 0 0
rz?c 0 (size varies per CD)
rz?d 0 0
rz?e 0 0
rz?f 0 0
rz?g 0 0
rz?h 0 0
RX23 partitions
disk start length
rz?a 0 2879
rz?b 0 0
rz?c 0 2879
rz?d 0 0
rz?e 0 0
rz?f 0 0
rz?g 0 0
rz?h 0 0
RX26 partitions
disk start length
rz?a 0 5759
rz?b 0 0
rz?c 0 5759
rz?d 0 0
rz?e 0 0
rz?f 0 0
rz?g 0 0
rz?h 0 0
RX33 partitions
disk start length
rz?a 0 2400
rz?b 0 0
rz?c 0 2400
rz?d 0 0
rz?e 0 0
rz?f 0 0
rz?g 0 0
rz?h 0 0
Usually, the rz?a partition is used for the root file system and the rz?b partition as a paging area. The rz?c partition is used for disk-
to-disk copying because it maps the entire disk.
Files
See Also
nbuf(4), dkio(4), SCSI(4), chpt(8), MAKEDEV(8), uerf(8)
rz(4)