re(7)re(7)NAMEre - SWXCR RAID interface
2100 Server Model A500MP DEC SWXCR controller xcrn at * vector xcintr
device disk renn at xcrn drive nn
The re driver is for the SWXCR RAID Array controller.
The following rules are used to determine the major and minor numbers
that are associated with an re type disk. There are two major numbers
used to represent re disks. The major numbers are 11 for block devices
and 44 for character (raw) devices.
The minor number is used to represent both the unit number and parti‐
tion. A disk partition refers to a designated portion of the physical
disk. To accomplish this reference, the 20-bit minor number is divided
into three parts. The lowest six bits of the minor number specify a
disk partition. The partitions use a letter, a through h, for their
The next three bits of the minor number specify the RE unit number for
a unit attached to an SWXCR controller. The final 11 bits specify the
The device special file names associated with re disks are based on
conventions that are closely associated with the minor number assigned
to the disk. The standard device names begin with re for block special
files and rre for character (raw) special files. Following the re is
the unit number and then a letter, a through h, that represents the
partition. Throughout this reference page, the question mark (?) char‐
acter represents the unit number in the name of the device special
file. For example, re?b could represent re0b, re1b, and so on.
The unit number can be calculated if the major and minor numbers of an
re disk are provided. For example, suppose you have a device special
file rre6a, with a major number of 44 and a minor number of 384. The
partition is represented by the lower six bits of the number 384.
These lower six bits of the number 384 are 0, which specifies the a
partition. The next three bits of the minor number 384 specify the
unit number, which is 6. The next eleven bits specify the controller
number, which is zero. Putting these three pieces together reveals that
the major/minor number pair 44/384 refers to the a partition of unit 6
attached to controller number 0.
A 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 capability 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
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. 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.
For systems with RE disks, the first software boot after the system is
powered on may take longer than expected. This delay is normal and is
caused by the software spinning up the RE disks.
The RE driver handles all disk drives that can be connected to the
SWXCR controller. To determine which drives are supported for specific
CPU types and hardware configurations, see the Installation and Config‐
uration Guide for the StorageWorks RAID Array 200 Subsystem Family.
SWXCR RAID Controllers are viewed in all cases as RE type disks. There
are some notable differences that should be taken into consideration
when configuring a RAID device: Currently only sector sizes of 512
bytes are supported. Logical Volume sizes are not fixed sizes as com‐
pared to other disk devices. The size of the Logical Volume is config‐
urable based on needs. The dynamic nature of Logical Volume sizes is
dealt with by defining RAID devices as DYNAMIC. Only partitions a, b,
c, and g are defined. If necessary, the disklabel(8) command can be
run to change and define partitions for RAID devices.
Usually, the re?a partition is used for the root file system and the
re?b partition as a paging area. The re?c partition can be used for
disk-to-disk copying because it maps the entire disk.
The starting location and length (in 512 byte sectors) of the disk par‐
titions of each drive are shown in the following table. Partition sizes
can be changed by using the disklabel(8) command.
SWXCR (RAID) partitions for systems based on the Alpha AXP architecture
disk start length
re?a 0 131072 re?b 131072 262144 re?c 0 end of
media re?d 0 0 re?e 0 0 re?f 0 0
re?g 393216 end of media re?h 0 0
SEE ALSOdisklabel(8), MAKEDEV(8), uerf(8)re(7)