Mylex DAC960/DAC1100 PCI RAID Controller Driver for Linux

                        Version 2.2.5 for Linux 2.2.14
                        Version 2.0.5 for Linux 2.0.38

                              PRODUCTION RELEASE

                                23 January 2000

                               Leonard N. Zubkoff
                               Dandelion Digital
                               lnz@dandelion.com

         Copyright 1998-2000 by Leonard N. Zubkoff <lnz@dandelion.com>


                                 INTRODUCTION

Mylex, Inc. designs and manufactures a variety of high performance PCI RAID
controllers.  Mylex Corporation is located at 34551 Ardenwood Blvd., Fremont,
California 94555, USA and can be reached at 510/796-6100 or on the World Wide
Web at http://www.mylex.com.  Mylex RAID Technical Support can be reached by
electronic mail at support@mylex.com (for eXtremeRAID 1100 and older DAC960
models) or techsup@mylex.com (for AcceleRAID models), by voice at 510/608-2400,
or by FAX at 510/745-7715.  Contact information for offices in Europe and Japan
is available on the Web site.

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
my Linux Home Page at URL "http://www.dandelion.com/Linux/".  The Linux DAC960
driver supports all current 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.

Bug reports should be sent via electronic mail to "lnz@dandelion.com".  Please
include with the bug report the complete configuration messages reported by the
driver at startup, along with any subsequent system messages relevant to the
controller's operation, and a detailed description of your system's hardware
configuration.

Please consult the DAC960 RAID controller documentation for detailed
information regarding installation and configuration of the controllers.  This
document primarily provides information specific to the Linux DAC960 support.


                                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.


                 SUPPORTED DAC960/DAC1100 PCI RAID CONTROLLERS

The following list comprises the supported DAC960 and DAC1100 PCI RAID
Controllers as of the date of this document.  It is recommended that anyone
purchasing a Mylex PCI RAID Controller not in the following table contact the
author beforehand to verify that it is or will be supported.  The eXtremeRAID
2000, eXtremeRAID 3000, and AcceleRAID 352 have an entirely new firmware
interface and are not yet supported by this driver.

eXtremeRAID 1100 (DAC1164P)
            3 Wide Ultra-2/LVD SCSI channels
            233MHz StrongARM SA 110 Processor
            64 Bit PCI (backward compatible with 32 Bit PCI slots)
            16MB/32MB/64MB Parity SDRAM Memory with Battery Backup

AcceleRAID 250 (DAC960PTL1)
            Uses onboard Symbios SCSI chips on certain motherboards
            Also includes one onboard Wide Ultra-2/LVD SCSI Channel
            66MHz Intel i960RD RISC Processor
            4MB/8MB/16MB/32MB/64MB/128MB ECC EDO Memory

AcceleRAID 200 (DAC960PTL0)
            Uses onboard Symbios SCSI chips on certain motherboards
            Includes no onboard SCSI Channels
            66MHz Intel i960RD RISC Processor
            4MB/8MB/16MB/32MB/64MB/128MB ECC EDO Memory

AcceleRAID 150 (DAC960PRL)
            Uses onboard Symbios SCSI chips on certain motherboards
            Also includes one onboard Wide Ultra-2/LVD SCSI Channel
            33MHz Intel i960RP RISC Processor
            4MB Parity EDO Memory

DAC960PJ    1/2/3 Wide Ultra SCSI-3 Channels
            66MHz Intel i960RD RISC Processor
            4MB/8MB/16MB/32MB/64MB/128MB ECC EDO Memory

DAC960PG    1/2/3 Wide Ultra SCSI-3 Channels
            33MHz Intel i960RP RISC Processor
            4MB/8MB ECC EDO Memory

DAC960PU    1/2/3 Wide Ultra SCSI-3 Channels
            Intel i960CF RISC Processor
            4MB/8MB EDRAM or 2MB/4MB/8MB/16MB/32MB DRAM Memory

DAC960PD    1/2/3 Wide Fast SCSI-2 Channels
            Intel i960CF RISC Processor
            4MB/8MB EDRAM or 2MB/4MB/8MB/16MB/32MB DRAM Memory

DAC960PL    1/2/3 Wide Fast SCSI-2 Channels
            Intel i960 RISC Processor
            2MB/4MB/8MB/16MB/32MB DRAM Memory

For the eXtremeRAID 1100, firmware version 5.06-0-52 or above is required.

For the AcceleRAID 250, 200, and 150, firmware version 4.06-0-57 or above is
required.

For the DAC960PJ and DAC960PG, firmware version 4.06-0-00 or above is required.

For the DAC960PU, DAC960PD, and DAC960PL, firmware version 3.51-0-04 or above
is required.

Note that earlier revisions of the DAC960PU, DAC960PD, and DAC960PL controllers
were delivered with version 2.xx firmware.  Version 2.xx firmware is not
supported by this driver and no support is envisioned.  Contact Mylex RAID
Technical Support to inquire about upgrading controllers with version 2.xx
firmware to version 3.51-0-04.  Upgrading to version 3.xx firmware requires
installation of higher capacity Flash ROM chips, and not all DAC960PD and
DAC960PL controllers can be upgraded.

Please note that not all SCSI disk drives are suitable for use with DAC960
controllers, and only particular firmware versions of any given model may
actually function correctly.  Similarly, not all motherboards have a BIOS that
properly initializes the AcceleRAID 250, AcceleRAID 200, AcceleRAID 150,
DAC960PJ, and DAC960PG because the Intel i960RD/RP is a multi-function device.
If in doubt, contact Mylex RAID Technical Support (support@mylex.com) to verify
compatibility.  Mylex makes available a hard disk compatibility list by FTP at
ftp://ftp.mylex.com/pub/dac960/diskcomp.html.


                              DRIVER INSTALLATION

This distribution was prepared for Linux kernel version 2.2.14 or 2.0.38.

To install the DAC960 RAID driver, you may use the following commands,
replacing "/usr/src" with wherever you keep your Linux kernel source tree:

  cd /usr/src
  tar -xvzf DAC960-2.2.5.tar.gz (or DAC960-2.0.5.tar.gz)
  mv README.DAC960 linux/Documentation
  mv DAC960.[ch] linux/drivers/block
  patch -p0 < DAC960.patch (driver 2.0.5 only)
  cd linux
  make config
  make depend
  make bzImage (or zImage)

Then install "arch/i386/boot/bzImage" or "arch/i386/boot/zImage" as your
standard kernel, run lilo if appropriate, and reboot.

To create the necessary devices in /dev, the "make_rd" script included in
"DAC960-Utilities.tar.gz" from http://www.dandelion.com/Linux/ may be used.
LILO 21 and FDISK v2.9 include DAC960 support; also included in this archive
are patches to LILO 20 and FDISK v2.8 that add DAC960 support, along with
statically linked executables of LILO and FDISK.  This modified version of LILO
will allow booting from a DAC960 controller and/or mounting the root file
system from a DAC960.

Red Hat Linux 6.0 and SuSE Linux 6.1 include support for Mylex PCI RAID
controllers.  Installing directly onto a DAC960 may be problematic from other
Linux distributions until their installation utilities are updated.


                              INSTALLATION NOTES

Before installing Linux or adding DAC960 logical drives to an existing Linux
system, the controller must first be configured to provide one or more logical
drives using the BIOS Configuration Utility or DACCF.  Please note that since
there are only at most 6 usable partitions on each logical drive, systems
requiring more partitions should subdivide a drive group into multiple logical
drives, each of which can have up to 6 partitions.  Also, note that with large
disk arrays it is advisable to enable the 8GB BIOS Geometry (255/63) rather
than accepting the default 2GB BIOS Geometry (128/32); failing to so do will
cause the logical drive geometry to have more than 65535 cylinders which will
make it impossible for FDISK to be used properly.  The 8GB BIOS Geometry can be
enabled by configuring the DAC960 BIOS, which is accessible via Alt-M during
the BIOS initialization sequence.

For maximum performance and the most efficient E2FSCK performance, it is
recommended that EXT2 file systems be built with a 4KB block size and 16 block
stride to match the DAC960 controller's 64KB default stripe size.  The command
"mke2fs -b 4096 -R stride=16 <device>" is appropriate.  Unless there will be a
large number of small files on the file systems, it is also beneficial to add
the "-i 16384" option to increase the bytes per inode parameter thereby
reducing the file system metadata.  Finally, on systems that will only be run
with Linux 2.2 or later kernels it is beneficial to enable sparse superblocks
with the "-s 1" option.


                      DAC960 ANNOUNCEMENTS MAILING LIST

The DAC960 Announcements Mailing List provides a forum for informing Linux
users of new driver releases and other announcements regarding Linux support
for DAC960 PCI RAID Controllers.  To join the mailing list, send a message to
"dac960-announce-request@dandelion.com" with the line "subscribe" in the
message body.


                CONTROLLER CONFIGURATION AND STATUS MONITORING

The DAC960 RAID controllers running firmware 4.06 or above include a Background
Initialization facility so that system downtime is minimized both for initial
installation and subsequent configuration of additional storage.  The BIOS
Configuration Utility (accessible via Alt-R during the BIOS initialization
sequence) is used to quickly configure the controller, and then the logical
drives that have been created are available for immediate use even while they
are still being initialized by the controller.  The primary need for online
configuration and status monitoring is then to avoid system downtime when disk
drives fail and must be replaced.  Mylex's online monitoring and configuration
utilities are being ported to Linux and will become available at some point in
the future.  Note that with a SAF-TE (SCSI Accessed Fault-Tolerant Enclosure)
enclosure, the controller is able to rebuild failed drives automatically as
soon as a drive replacement is made available.

The primary interfaces for controller configuration and status monitoring are
special files created in the /proc/rd/... hierarchy along with the normal
system console logging mechanism.  Whenever the system is operating, the DAC960
driver queries each controller for status information every 10 seconds, and
checks for additional conditions every 60 seconds.  The initial status of each
controller is always available for controller N in /proc/rd/cN/initial_status,
and the current status as of the last status monitoring query is available in
/proc/rd/cN/current_status.  In addition, status changes are also logged by the
driver to the system console and will appear in the log files maintained by
syslog.  The progress of asynchronous rebuild or consistency check operations
is also available in /proc/rd/cN/current_status, and progress messages are
logged to the system console at most every 60 seconds.

Starting with the 2.2.3/2.0.3 versions of the driver, the status information
available in /proc/rd/cN/initial_status and /proc/rd/cN/current_status has been
augmented to include the vendor, model, revision, and serial number (if
available) for each physical device found connected to the controller:

***** DAC960 RAID Driver Version 2.2.3 of 19 August 1999 *****
Copyright 1998-1999 by Leonard N. Zubkoff <lnz@dandelion.com>
Configuring Mylex DAC960PRL PCI RAID Controller
  Firmware Version: 4.07-0-07, Channels: 1, Memory Size: 16MB
  PCI Bus: 1, Device: 4, Function: 1, I/O Address: Unassigned
  PCI Address: 0xFE300000 mapped at 0xA0800000, IRQ Channel: 21
  Controller Queue Depth: 128, Maximum Blocks per Command: 128
  Driver Queue Depth: 127, Maximum Scatter/Gather Segments: 33
  Stripe Size: 64KB, Segment Size: 8KB, BIOS Geometry: 255/63
  SAF-TE Enclosure Management Enabled
  Physical Devices:
    0:0  Vendor: IBM       Model: DRVS09D           Revision: 0270
         Serial Number:       68016775HA
         Disk Status: Online, 17928192 blocks
    0:1  Vendor: IBM       Model: DRVS09D           Revision: 0270
         Serial Number:       68004E53HA
         Disk Status: Online, 17928192 blocks
    0:2  Vendor: IBM       Model: DRVS09D           Revision: 0270
         Serial Number:       13013935HA
         Disk Status: Online, 17928192 blocks
    0:3  Vendor: IBM       Model: DRVS09D           Revision: 0270
         Serial Number:       13016897HA
         Disk Status: Online, 17928192 blocks
    0:4  Vendor: IBM       Model: DRVS09D           Revision: 0270
         Serial Number:       68019905HA
         Disk Status: Online, 17928192 blocks
    0:5  Vendor: IBM       Model: DRVS09D           Revision: 0270
         Serial Number:       68012753HA
         Disk Status: Online, 17928192 blocks
    0:6  Vendor: ESG-SHV   Model: SCA HSBP M6       Revision: 0.61
  Logical Drives:
    /dev/rd/c0d0: RAID-5, Online, 89640960 blocks, Write Thru
  No Rebuild or Consistency Check in Progress

To simplify the monitoring process for custom software, the special file
/proc/rd/status returns "OK" when all DAC960 controllers in the system are
operating normally and no failures have occurred, or "ALERT" if any logical
drives are offline or critical or any non-standby physical drives are dead.

Configuration commands for controller N are available via the special file
/proc/rd/cN/user_command.  A human readable command can be written to this
special file to initiate a configuration operation, and the results of the
operation can then be read back from the special file in addition to being
logged to the system console.  The shell command sequence

  echo "<configuration-command>" > /proc/rd/c0/user_command
  cat /proc/rd/c0/user_command

is typically used to execute configuration commands.  The configuration
commands are:

  flush-cache

    The "flush-cache" command flushes the controller's cache.  The system
    automatically flushes the cache at shutdown or if the driver module is
    unloaded, so this command is only needed to be certain a write back cache
    is flushed to disk before the system is powered off by a command to a UPS.
    Note that the flush-cache command also stops an asynchronous rebuild or
    consistency check, so it should not be used except when the system is being
    halted.

  kill <channel>:<target-id>

    The "kill" command marks the physical drive <channel>:<target-id> as DEAD.
    This command is provided primarily for testing, and should not be used
    during normal system operation.

  make-online <channel>:<target-id>

    The "make-online" command changes the physical drive <channel>:<target-id>
    from status DEAD to status ONLINE.  In cases where multiple physical drives
    have been killed simultaneously, this command may be used to bring them
    back online, after which a consistency check is advisable.

    Warning: make-online should only be used on a dead physical drive that is
    an active part of a drive group, never on a standby drive.

  make-standby <channel>:<target-id>

    The "make-standby" command changes physical drive <channel>:<target-id>
    from status DEAD to status STANDBY.  It should only be used in cases where
    a dead drive was replaced after an automatic rebuild was performed onto a
    standby drive.  It cannot be used to add a standby drive to the controller
    configuration if one was not created initially; the BIOS Configuration
    Utility must be used for that currently.

  rebuild <channel>:<target-id>

    The "rebuild" command initiates an asynchronous rebuild onto physical drive
    <channel>:<target-id>.  It should only be used when a dead drive has been
    replaced.

  check-consistency <logical-drive-number>

    The "check-consistency" command initiates an asynchronous consistency check
    of <logical-drive-number> with automatic restoration.  It can be used
    whenever it is desired to verify the consistency of the redundancy
    information.

  cancel-rebuild
  cancel-consistency-check

    The "cancel-rebuild" and "cancel-consistency-check" commands cancel any
    rebuild or consistency check operations previously initiated.


               EXAMPLE I - DRIVE FAILURE WITHOUT A STANDBY DRIVE

The following annotated logs demonstrate the controller configuration and and
online status monitoring capabilities of the Linux DAC960 Driver.  The test
configuration comprises 6 1GB Quantum Atlas I disk drives on two channels of a
DAC960PJ controller.  The physical drives are configured into a single drive
group without a standby drive, and the drive group has been configured into two
logical drives, one RAID-5 and one RAID-6.  Note that these logs are from an
earlier version of the driver and the messages have changed somewhat with newer
releases, but the functionality remains similar.  First, here is the current
status of the RAID configuration:

gwynedd:/u/lnz# cat /proc/rd/c0/current_status
***** DAC960 RAID Driver Version 2.0.0 of 23 March 1999 *****
Copyright 1998-1999 by Leonard N. Zubkoff <lnz@dandelion.com>
Configuring Mylex DAC960PJ PCI RAID Controller
  Firmware Version: 4.06-0-08, Channels: 3, Memory Size: 8MB
  PCI Bus: 0, Device: 19, Function: 1, I/O Address: Unassigned
  PCI Address: 0xFD4FC000 mapped at 0x8807000, IRQ Channel: 9
  Controller Queue Depth: 128, Maximum Blocks per Command: 128
  Driver Queue Depth: 127, Maximum Scatter/Gather Segments: 33
  Stripe Size: 64KB, Segment Size: 8KB, BIOS Geometry: 255/63
  Physical Devices:
    0:1 - Disk: Online, 2201600 blocks
    0:2 - Disk: Online, 2201600 blocks
    0:3 - Disk: Online, 2201600 blocks
    1:1 - Disk: Online, 2201600 blocks
    1:2 - Disk: Online, 2201600 blocks
    1:3 - Disk: Online, 2201600 blocks
  Logical Drives:
    /dev/rd/c0d0: RAID-5, Online, 5498880 blocks, Write Thru
    /dev/rd/c0d1: RAID-6, Online, 3305472 blocks, Write Thru
  No Rebuild or Consistency Check in Progress

gwynedd:/u/lnz# cat /proc/rd/status
OK

The above messages indicate that everything is healthy, and /proc/rd/status
returns "OK" indicating that there are no problems with any DAC960 controller
in the system.  For demonstration purposes, while I/O is active Physical Drive
1:1 is now disconnected, simulating a drive failure.  The failure is noted by
the driver within 10 seconds of the controller's having detected it, and the
driver logs the following console status messages indicating that Logical
Drives 0 and 1 are now CRITICAL as a result of Physical Drive 1:1 being DEAD:

DAC960#0: Physical Drive 1:2 Error Log: Sense Key = 6, ASC = 29, ASCQ = 02
DAC960#0: Physical Drive 1:3 Error Log: Sense Key = 6, ASC = 29, ASCQ = 02
DAC960#0: Physical Drive 1:1 killed because of timeout on SCSI command
DAC960#0: Physical Drive 1:1 is now DEAD
DAC960#0: Logical Drive 0 (/dev/rd/c0d0) is now CRITICAL
DAC960#0: Logical Drive 1 (/dev/rd/c0d1) is now CRITICAL

The Sense Keys logged here are just Check Condition / Unit Attention conditions
arising from a SCSI bus reset that is forced by the controller during its error
recovery procedures.  Concurrently with the above, the driver status available
from /proc/rd also reflects the drive failure.  The status message in
/proc/rd/status has changed from "OK" to "ALERT":

gwynedd:/u/lnz# cat /proc/rd/status
ALERT

and /proc/rd/c0/current_status has been updated:

gwynedd:/u/lnz# cat /proc/rd/c0/current_status
  ...
  Physical Devices:
    0:1 - Disk: Online, 2201600 blocks
    0:2 - Disk: Online, 2201600 blocks
    0:3 - Disk: Online, 2201600 blocks
    1:1 - Disk: Dead, 2201600 blocks
    1:2 - Disk: Online, 2201600 blocks
    1:3 - Disk: Online, 2201600 blocks
  Logical Drives:
    /dev/rd/c0d0: RAID-5, Critical, 5498880 blocks, Write Thru
    /dev/rd/c0d1: RAID-6, Critical, 3305472 blocks, Write Thru
  No Rebuild or Consistency Check in Progress

Since there are no standby drives configured, the system can continue to access
the logical drives in a performance degraded mode until the failed drive is
replaced and a rebuild operation completed to restore the redundancy of the
logical drives.  Once Physical Drive 1:1 is replaced with a properly
functioning drive, or if the physical drive was killed without having failed
(e.g., due to electrical problems on the SCSI bus), the user can instruct the
controller to initiate a rebuild operation onto the newly replaced drive:

gwynedd:/u/lnz# echo "rebuild 1:1" > /proc/rd/c0/user_command
gwynedd:/u/lnz# cat /proc/rd/c0/user_command
Rebuild of Physical Drive 1:1 Initiated

The echo command instructs the controller to initiate an asynchronous rebuild
operation onto Physical Drive 1:1, and the status message that results from the
operation is then available for reading from /proc/rd/c0/user_command, as well
as being logged to the console by the driver.

Within 10 seconds of this command the driver logs the initiation of the
asynchronous rebuild operation:

DAC960#0: Rebuild of Physical Drive 1:1 Initiated
DAC960#0: Physical Drive 1:1 Error Log: Sense Key = 6, ASC = 29, ASCQ = 01
DAC960#0: Physical Drive 1:1 is now WRITE-ONLY
DAC960#0: Rebuild in Progress: Logical Drive 0 (/dev/rd/c0d0) 1% completed

and /proc/rd/c0/current_status is updated:

gwynedd:/u/lnz# cat /proc/rd/c0/current_status
  ...
  Physical Devices:
    0:1 - Disk: Online, 2201600 blocks
    0:2 - Disk: Online, 2201600 blocks
    0:3 - Disk: Online, 2201600 blocks
    1:1 - Disk: Write-Only, 2201600 blocks
    1:2 - Disk: Online, 2201600 blocks
    1:3 - Disk: Online, 2201600 blocks
  Logical Drives:
    /dev/rd/c0d0: RAID-5, Critical, 5498880 blocks, Write Thru
    /dev/rd/c0d1: RAID-6, Critical, 3305472 blocks, Write Thru
  Rebuild in Progress: Logical Drive 0 (/dev/rd/c0d0) 6% completed

As the rebuild progresses, the current status in /proc/rd/c0/current_status is
updated every 10 seconds:

gwynedd:/u/lnz# cat /proc/rd/c0/current_status
  ...
  Physical Devices:
    0:1 - Disk: Online, 2201600 blocks
    0:2 - Disk: Online, 2201600 blocks
    0:3 - Disk: Online, 2201600 blocks
    1:1 - Disk: Write-Only, 2201600 blocks
    1:2 - Disk: Online, 2201600 blocks
    1:3 - Disk: Online, 2201600 blocks
  Logical Drives:
    /dev/rd/c0d0: RAID-5, Critical, 5498880 blocks, Write Thru
    /dev/rd/c0d1: RAID-6, Critical, 3305472 blocks, Write Thru
  Rebuild in Progress: Logical Drive 0 (/dev/rd/c0d0) 15% completed

and every minute a progress message is logged to the console by the driver:

DAC960#0: Rebuild in Progress: Logical Drive 0 (/dev/rd/c0d0) 32% completed
DAC960#0: Rebuild in Progress: Logical Drive 0 (/dev/rd/c0d0) 63% completed
DAC960#0: Rebuild in Progress: Logical Drive 0 (/dev/rd/c0d0) 94% completed
DAC960#0: Rebuild in Progress: Logical Drive 1 (/dev/rd/c0d1) 94% completed

Finally, the rebuild completes successfully.  The driver logs the status of the 
logical and physical drives and the rebuild completion:

DAC960#0: Rebuild Completed Successfully
DAC960#0: Physical Drive 1:1 is now ONLINE
DAC960#0: Logical Drive 0 (/dev/rd/c0d0) is now ONLINE
DAC960#0: Logical Drive 1 (/dev/rd/c0d1) is now ONLINE

/proc/rd/c0/current_status is updated:

gwynedd:/u/lnz# cat /proc/rd/c0/current_status
  ...
  Physical Devices:
    0:1 - Disk: Online, 2201600 blocks
    0:2 - Disk: Online, 2201600 blocks
    0:3 - Disk: Online, 2201600 blocks
    1:1 - Disk: Online, 2201600 blocks
    1:2 - Disk: Online, 2201600 blocks
    1:3 - Disk: Online, 2201600 blocks
  Logical Drives:
    /dev/rd/c0d0: RAID-5, Online, 5498880 blocks, Write Thru
    /dev/rd/c0d1: RAID-6, Online, 3305472 blocks, Write Thru
  Rebuild Completed Successfully

and /proc/rd/status indicates that everything is healthy once again:

gwynedd:/u/lnz# cat /proc/rd/status
OK


                EXAMPLE II - DRIVE FAILURE WITH A STANDBY DRIVE

The following annotated logs demonstrate the controller configuration and and
online status monitoring capabilities of the Linux DAC960 Driver.  The test
configuration comprises 6 1GB Quantum Atlas I disk drives on two channels of a
DAC960PJ controller.  The physical drives are configured into a single drive
group with a standby drive, and the drive group has been configured into two
logical drives, one RAID-5 and one RAID-6.  Note that these logs are from an
earlier version of the driver and the messages have changed somewhat with newer
releases, but the functionality remains similar.  First, here is the current
status of the RAID configuration:

gwynedd:/u/lnz# cat /proc/rd/c0/current_status
***** DAC960 RAID Driver Version 2.0.0 of 23 March 1999 *****
Copyright 1998-1999 by Leonard N. Zubkoff <lnz@dandelion.com>
Configuring Mylex DAC960PJ PCI RAID Controller
  Firmware Version: 4.06-0-08, Channels: 3, Memory Size: 8MB
  PCI Bus: 0, Device: 19, Function: 1, I/O Address: Unassigned
  PCI Address: 0xFD4FC000 mapped at 0x8807000, IRQ Channel: 9
  Controller Queue Depth: 128, Maximum Blocks per Command: 128
  Driver Queue Depth: 127, Maximum Scatter/Gather Segments: 33
  Stripe Size: 64KB, Segment Size: 8KB, BIOS Geometry: 255/63
  Physical Devices:
    0:1 - Disk: Online, 2201600 blocks
    0:2 - Disk: Online, 2201600 blocks
    0:3 - Disk: Online, 2201600 blocks
    1:1 - Disk: Online, 2201600 blocks
    1:2 - Disk: Online, 2201600 blocks
    1:3 - Disk: Standby, 2201600 blocks
  Logical Drives:
    /dev/rd/c0d0: RAID-5, Online, 4399104 blocks, Write Thru
    /dev/rd/c0d1: RAID-6, Online, 2754560 blocks, Write Thru
  No Rebuild or Consistency Check in Progress

gwynedd:/u/lnz# cat /proc/rd/status
OK

The above messages indicate that everything is healthy, and /proc/rd/status
returns "OK" indicating that there are no problems with any DAC960 controller
in the system.  For demonstration purposes, while I/O is active Physical Drive
1:2 is now disconnected, simulating a drive failure.  The failure is noted by
the driver within 10 seconds of the controller's having detected it, and the
driver logs the following console status messages:

DAC960#0: Physical Drive 1:1 Error Log: Sense Key = 6, ASC = 29, ASCQ = 02
DAC960#0: Physical Drive 1:3 Error Log: Sense Key = 6, ASC = 29, ASCQ = 02
DAC960#0: Physical Drive 1:2 killed because of timeout on SCSI command
DAC960#0: Physical Drive 1:2 is now DEAD
DAC960#0: Physical Drive 1:2 killed because it was removed
DAC960#0: Logical Drive 0 (/dev/rd/c0d0) is now CRITICAL
DAC960#0: Logical Drive 1 (/dev/rd/c0d1) is now CRITICAL

Since a standby drive is configured, the controller automatically begins
rebuilding onto the standby drive:

DAC960#0: Physical Drive 1:3 is now WRITE-ONLY
DAC960#0: Rebuild in Progress: Logical Drive 0 (/dev/rd/c0d0) 4% completed

Concurrently with the above, the driver status available from /proc/rd also
reflects the drive failure and automatic rebuild.  The status message in
/proc/rd/status has changed from "OK" to "ALERT":

gwynedd:/u/lnz# cat /proc/rd/status
ALERT

and /proc/rd/c0/current_status has been updated:

gwynedd:/u/lnz# cat /proc/rd/c0/current_status
  ...
  Physical Devices:
    0:1 - Disk: Online, 2201600 blocks
    0:2 - Disk: Online, 2201600 blocks
    0:3 - Disk: Online, 2201600 blocks
    1:1 - Disk: Online, 2201600 blocks
    1:2 - Disk: Dead, 2201600 blocks
    1:3 - Disk: Write-Only, 2201600 blocks
  Logical Drives:
    /dev/rd/c0d0: RAID-5, Critical, 4399104 blocks, Write Thru
    /dev/rd/c0d1: RAID-6, Critical, 2754560 blocks, Write Thru
  Rebuild in Progress: Logical Drive 0 (/dev/rd/c0d0) 4% completed

As the rebuild progresses, the current status in /proc/rd/c0/current_status is
updated every 10 seconds:

gwynedd:/u/lnz# cat /proc/rd/c0/current_status
  ...
  Physical Devices:
    0:1 - Disk: Online, 2201600 blocks
    0:2 - Disk: Online, 2201600 blocks
    0:3 - Disk: Online, 2201600 blocks
    1:1 - Disk: Online, 2201600 blocks
    1:2 - Disk: Dead, 2201600 blocks
    1:3 - Disk: Write-Only, 2201600 blocks
  Logical Drives:
    /dev/rd/c0d0: RAID-5, Critical, 4399104 blocks, Write Thru
    /dev/rd/c0d1: RAID-6, Critical, 2754560 blocks, Write Thru
  Rebuild in Progress: Logical Drive 0 (/dev/rd/c0d0) 40% completed

and every minute a progress message is logged on the console by the driver:

DAC960#0: Rebuild in Progress: Logical Drive 0 (/dev/rd/c0d0) 40% completed
DAC960#0: Rebuild in Progress: Logical Drive 0 (/dev/rd/c0d0) 76% completed
DAC960#0: Rebuild in Progress: Logical Drive 1 (/dev/rd/c0d1) 66% completed
DAC960#0: Rebuild in Progress: Logical Drive 1 (/dev/rd/c0d1) 84% completed

Finally, the rebuild completes successfully.  The driver logs the status of the 
logical and physical drives and the rebuild completion:

DAC960#0: Rebuild Completed Successfully
DAC960#0: Physical Drive 1:3 is now ONLINE
DAC960#0: Logical Drive 0 (/dev/rd/c0d0) is now ONLINE
DAC960#0: Logical Drive 1 (/dev/rd/c0d1) is now ONLINE

/proc/rd/c0/current_status is updated:

***** DAC960 RAID Driver Version 2.0.0 of 23 March 1999 *****
Copyright 1998-1999 by Leonard N. Zubkoff <lnz@dandelion.com>
Configuring Mylex DAC960PJ PCI RAID Controller
  Firmware Version: 4.06-0-08, Channels: 3, Memory Size: 8MB
  PCI Bus: 0, Device: 19, Function: 1, I/O Address: Unassigned
  PCI Address: 0xFD4FC000 mapped at 0x8807000, IRQ Channel: 9
  Controller Queue Depth: 128, Maximum Blocks per Command: 128
  Driver Queue Depth: 127, Maximum Scatter/Gather Segments: 33
  Stripe Size: 64KB, Segment Size: 8KB, BIOS Geometry: 255/63
  Physical Devices:
    0:1 - Disk: Online, 2201600 blocks
    0:2 - Disk: Online, 2201600 blocks
    0:3 - Disk: Online, 2201600 blocks
    1:1 - Disk: Online, 2201600 blocks
    1:2 - Disk: Dead, 2201600 blocks
    1:3 - Disk: Online, 2201600 blocks
  Logical Drives:
    /dev/rd/c0d0: RAID-5, Online, 4399104 blocks, Write Thru
    /dev/rd/c0d1: RAID-6, Online, 2754560 blocks, Write Thru
  Rebuild Completed Successfully

and /proc/rd/status indicates that everything is healthy once again:

gwynedd:/u/lnz# cat /proc/rd/status
OK

Note that the absence of a viable standby drive does not create an "ALERT"
status.  Once dead Physical Drive 1:2 has been replaced, the controller must be
told that this has occurred and that the newly replaced drive should become the
new standby drive:

gwynedd:/u/lnz# echo "make-standby 1:2" > /proc/rd/c0/user_command
gwynedd:/u/lnz# cat /proc/rd/c0/user_command
Make Standby of Physical Drive 1:2 Succeeded

The echo command instructs the controller to make Physical Drive 1:2 into a
standby drive, and the status message that results from the operation is then
available for reading from /proc/rd/c0/user_command, as well as being logged to
the console by the driver.  Within 60 seconds of this command the driver logs:

DAC960#0: Physical Drive 1:2 Error Log: Sense Key = 6, ASC = 29, ASCQ = 01
DAC960#0: Physical Drive 1:2 is now STANDBY
DAC960#0: Make Standby of Physical Drive 1:2 Succeeded

and /proc/rd/c0/current_status is updated:

gwynedd:/u/lnz# cat /proc/rd/c0/current_status
  ...
  Physical Devices:
    0:1 - Disk: Online, 2201600 blocks
    0:2 - Disk: Online, 2201600 blocks
    0:3 - Disk: Online, 2201600 blocks
    1:1 - Disk: Online, 2201600 blocks
    1:2 - Disk: Standby, 2201600 blocks
    1:3 - Disk: Online, 2201600 blocks
  Logical Drives:
    /dev/rd/c0d0: RAID-5, Online, 4399104 blocks, Write Thru
    /dev/rd/c0d1: RAID-6, Online, 2754560 blocks, Write Thru
  Rebuild Completed Successfully