rz(4)

Name

rz − SCSI disk interface

Syntax

rz0 at scsi0 slave 0 (RZ23)
rz2 at sii0 slave 2 (RZ55)
rz6 at asc0 slave 6 (RZ55)

Description

This is a driver for all DIGITAL SCSI disk drives.

The following rules are used to determine the major and minor numbers which are associated with an rz type disk. There is one major number used to represent rz 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 eight bit minor number is broken up into two parts. The low three bits of the minor number specifies a disk partition. These three bits allow for the naming of eight partitions. The partitions are named a,b,c,d,e,f,g and h. The upper five bits of the minor number specifies the SCSI unit number within a group of 32 disks.

The device special file names associated with rz 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 rz for the block special file and rrz for the raw (character) special file. Following the rz is the logical unit number and then a letter a through h to represent the partition. Through out this reference page the 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 rz disk. For the device special file rrz6a the major number is 56 and the minor number is 48. The partition is represented by the low 3 bits of the number 48. The low 3 bits will be 0 which specifies the "a" partition. The upper 5 bits of 48 specifies the number 6. The major number is 56. Since 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 may break up large read and write requests into smaller fixed size transfers to the disk.

The character special file provides a raw interface which allows for direct transmission between the disk and the user’s read or write buffer. 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 should be a multiple of 512 bytes (a disk sector). Likewise, seek calls should 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 nbuf() for more information.)

Disk Support

This driver handles all disk drives that may be connected to the SCSI bus. Consult the ULTRIX Software Product Description to determine which controllers 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 chpt(.). For further information, see dkio(.).

RZ22 partitions
diskstartlength
rz?a032768
rz?b3276869664
rz?c0102431
rz?d00
rz?e00
rz?f00
rz?g00
rz?h00

RZ23 partitions
diskstartlength
rz?a032768
rz?b3276866690
rz?c0204864
rz?d9945835135
rz?e13459335135
rz?f16972835136
rz?g99458105406
rz?h13459370271

RZ24 partitions
diskstartlength
rz?a032768
rz?b32768131072
rz?c0409792
rz?d16384081984
rz?e24582481984
rz?f32780881984
rz?g163840245952
rz?h00

RZ55 partitions
diskstartlength
rz?a032768
rz?b32768131072
rz?c0649040
rz?d163840152446
rz?e316286152446
rz?f468732180308
rz?g163840485200
rz?h00

RZ56 partitions
diskstartlength
rz?a032768
rz?b32768131072
rz?c01299174
rz?d163840292530
rz?e456370292530
rz?f748900550273
rz?g1638401135334
rz?h731506567668

RZ57 partitions
diskstartlength
rz?a032768
rz?b32768184320
rz?c02025788
rz?d831488299008
rz?e1130496299008
rz?f1429504596284
rz?g217088614400
rz?h8314881194300

RRD40 (read only) partitions
diskstartlength
rz?a01171875
rz?b00
rz?c01171875
rz?d00
rz?e00
rz?f00
rz?g00
rz?h00

RX23 partitions
diskstartlength
rz?a02879
rz?b00
rz?c02879
rz?d00
rz?e00
rz?f00
rz?g00
rz?h00

Usually the rz?a partition is used for the root file system, the rz?b partition as a paging area. The rz?c partition for pack to pack copying because it maps the entire disk.

Files

/dev/rz???
/dev/rrz???

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