INTRODUCTION
The latest information on Linux support
for DAC960 PCI RAID Controllers, as
well as the most recent release of this
driver, will always be available from
Lenord Zubkoff's Home Page at URL
"http://www.dandelion.com/Linux/". 
The Linux DAC960 driver supports all
DAC960 PCI family controllers including
the AcceleRAID models, as well as the
eXtremeRAID 1100; see below for a complete
list.  For simplicity, in most places
this documentation refers to DAC960
generically rather than explicitly
listing all the models.
Driver features
The DAC960 RAID controllers are supported
solely as high performance RAID controllers,
not as interfaces to arbitrary SCSI
devices. The Linux DAC960 driver operates
at the block device level, the same level
as the SCSI and IDE drivers.  Unlike other
RAID controllers currently supported on
Linux, The DAC960 driver is not dependent
on the SCSI subsystem, and hence avoids
all the complexity and unnecessary code
that would be associated with an
implementation as a SCSI driver.  The
DAC960 driver is designed for as high
a performance as possible with no
compromises or extra code for
compatibility with lower performance
devices.  The DAC960 driver includes
extensive error logging and online
configuration management capabilities.
Except for initial configuration of the
controller and adding new disk drives,
most everything can be handled from Linux
while the system is operational.

The DAC960 driver is architected to
support up to 8 controllers per system.
Each DAC960 controller can support up
to 15 disk drives per channel, for a
maximum of 45 drives on a three channel
controller.  The drives installed on a
controller are divided into one or more
"Drive Groups", and then each Drive
Group is subdivided further into 1
to 32 "Logical Drives".  Each Logical
Drive has a specific RAID Level and
caching policy associated with it, and
it appears to Linux as a single block
device.  Logical Drives are further
subdivided into up to 7 partitions
through the normal Linux and PC disk
partitioning schemes. Logical Drives
are also known as "System Drives",
and Drive Groups are also called
"Packs".  Both terms are in use in
the Mylex documentation; I have
chosen to standardize on the more
generic "Logical Drive" and "Drive
Group".

DAC960 RAID disk devices are named
in the style of the Device File System
(DEVFS).  The device corresponding
to Logical Drive D on Controller C is
referred to as /dev/rd/cCdD, and the
 partitions are called /dev/rd/cCdDp1
through /dev/rd/cCdDp7.  For example,
partition 3 of Logical Drive 5 on
Controller 2 is referred to as
/dev/rd/c2d5p3.  Note that unlike 
with SCSI disks the device names will
not change in the event of a disk drive
failure. The DAC960 driver is assigned
major numbers 48 - 55 with one major
number per controller.  The 8 bits
of minor number are divided into
5 bits for the Logical Drive and
3 bits for the partition.
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