ri - I2O RAID disk interface
bus i2o0 at pci2001 slot 4
controller i2o_bs0 at i2o0 slot 18
The ri driver supports 32-bit and 64-bit PCI backplane
RAID controllers with Intelligent I/O (I2O) host interface
supporting backend SCSI channels. I2O is an open architecture
for developing device drivers that is independent
of the operating system, processor platform, and system
I/O bus. The communication model is based on a messagepassing
protocol reducing the number of driver interfaces
needed. A single driver called an Operating System Module(OSM)
is provided to support all Block Storage class
devices. Any RAID system that supports the I2O interface
functions with this driver. These devices are designated
as ri to distinguish them from ra, re, and rz (SCSI)
The StorageWorks Command Console Utility (SWCC) is supported
for online configuration and monitoring of I2O raid
The following rules are used to determine the major and
minor numbers that are associated with an ri type disk. A
dynamic major number is used to represent ri block
devices, and is assigned during initial configuration. The
current major number can be determined using the following
# /sbin/devswmgr -getnum i2o_bs
The preceding command displays the driver switch reservation
list, showing the device instance and major number
for the i2o_bs driver. An alternative method is:
# /sbin/sysconfig -q i2o_bs
The highest 14 bits of the 20-bit minor number represents
a particular Block Storage device, while lowest six bits
of the minor number specify disk partitions (identified by
the letters, a through h) on that device.
The device special file names associated with ri disks are
based on conventions that are closely associated with the
minor number assigned to the disk. The standard device
names begin with ri for block special files and rri for
character (raw) special files. Following the ri is the
unit number and then a letter, a through h, that represents
the partition. Throughout this reference page, the
question mark (?) character represents the unit number in
the name of the device special file. For example, ri?b
could represent ri0b, ri1b, and so on.
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 disk.
The character special file provides a raw interface that
allows for direct transmission between the disk and the
user's read or write buffer. A single read/write operation
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 ri 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 ri disks.
Disk Support [Toc] [Back]
The ri driver handles all disk drives that can be connected
to the I2O RAID controller. To determine which
drives are supported for specific CPU types and hardware
configurations, see the hardware installation and configuration
information for your I2O system.
I2O RAID Controllers are viewed in all cases as RI 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 compared to
other disk devices. The size of the Logical Volume is
configurable 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 ri?a partition is used for the root file system
and the ri?b partition as a paging area. The ri?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 partitions of each drive are shown in the following
table. Partition sizes can be changed by using the
I2O RAID partitions for systems based on the Alpha AXP
disk start length ri?a 0 131072
ri?b 131072 262144 ri?c 0 end of media
ri?d 0 0 ri?e 0 0 ri?f 0 0
ri?g 393216 end of media ri?h 0 0
RAID(7), SCSI(7), tz(7), rz(7), disklabel(8), MAKEDEV(8),
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