Linux Driver for Mylex DAC960/AcceleRAID/eXtremeRAID PCI RAID Controllers
  
  			Version 2.2.11 for Linux 2.2.19
  			Version 2.4.11 for Linux 2.4.12
  
  			      PRODUCTION RELEASE
  
  				11 October 2001
  
  			       Leonard N. Zubkoff
  			       Dandelion Digital
  			       lnz@dandelion.com
  
  	 Copyright 1998-2001 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 Technical Support can be reached by
  electronic mail at mylexsup@us.ibm.com, by voice at 510.608.2400, or by FAX at
  510.745.7715.  Contact information for offices in Europe and Japan is available
  on their 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 Mylex PCI RAID controllers including the new
  eXtremeRAID 2000/3000 and AcceleRAID 352/170/160 models which have an entirely
  new firmware interface from the older eXtremeRAID 1100, AcceleRAID 150/200/250,
  and DAC960PJ/PG/PU/PD/PL.  See below for a complete controller list as well as
  minimum firmware version requirements.  For simplicity, in most places this
  documentation refers to DAC960 generically rather than explicitly listing all
  the supported models.
  
  Driver 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.  Driver bugs are actually quite rare; if you encounter
  problems with disks being marked offline, for example, please contact Mylex
  Technical Support as the problem is related to the hardware configuration
  rather than the Linux driver.
  
  Please consult the RAID controller documentation for detailed information
  regarding installation and configuration of the controllers.  This document
  primarily provides information specific to the Linux 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 parallel SCSI controller can support up to 15 disk drives per
  channel, for a maximum of 60 drives on a four channel controller; the fibre
  channel eXtremeRAID 3000 controller supports up to 125 disk drives per loop for
  a total of 250 drives.  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 obsolete 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/AcceleRAID/eXtremeRAID PCI RAID CONTROLLERS
  
  The following list comprises the supported DAC960, AcceleRAID, and eXtremeRAID
  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.
  
  eXtremeRAID 3000
  	    1 Wide Ultra-2/LVD SCSI channel
  	    2 External Fibre FC-AL channels
  	    233MHz StrongARM SA 110 Processor
  	    64 Bit 33MHz PCI (backward compatible with 32 Bit PCI slots)
  	    32MB/64MB ECC SDRAM Memory
  
  eXtremeRAID 2000
  	    4 Wide Ultra-160 LVD SCSI channels
  	    233MHz StrongARM SA 110 Processor
  	    64 Bit 33MHz PCI (backward compatible with 32 Bit PCI slots)
  	    32MB/64MB ECC SDRAM Memory
  
  AcceleRAID 352
  	    2 Wide Ultra-160 LVD SCSI channels
  	    100MHz Intel i960RN RISC Processor
  	    64 Bit 33MHz PCI (backward compatible with 32 Bit PCI slots)
  	    32MB/64MB ECC SDRAM Memory
  
  AcceleRAID 170
  	    1 Wide Ultra-160 LVD SCSI channel
  	    100MHz Intel i960RM RISC Processor
  	    16MB/32MB/64MB ECC SDRAM Memory
  
  AcceleRAID 160 (AcceleRAID 170LP)
  	    1 Wide Ultra-160 LVD SCSI channel
  	    100MHz Intel i960RS RISC Processor
  	    Built in 16M ECC SDRAM Memory
  	    PCI Low Profile Form Factor - fit for 2U height
  
  eXtremeRAID 1100 (DAC1164P)
  	    3 Wide Ultra-2/LVD SCSI channels
  	    233MHz StrongARM SA 110 Processor
  	    64 Bit 33MHz 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
  
  DAC960P	    1/2/3 Wide Fast SCSI-2 Channels
  	    Intel i960 RISC Processor
  	    2MB/4MB/8MB/16MB/32MB DRAM Memory
  
  For the eXtremeRAID 2000/3000 and AcceleRAID 352/170/160, firmware version
  6.00-01 or above is required.
  
  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, DAC960PL, and DAC960P, either firmware version
  3.51-0-04 or above is required (for dual Flash ROM controllers), or firmware
  version 2.73-0-00 or above is required (for single Flash ROM controllers)
  
  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 (mylexsup@us.ibm.com) to
  verify compatibility.  Mylex makes available a hard disk compatibility list at
  http://www.mylex.com/support/hdcomp/hd-lists.html.
  
  
  			      DRIVER INSTALLATION
  
  This distribution was prepared for Linux kernel version 2.2.19 or 2.4.12.
  
  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 DAC960-2.2.11.tar.gz (or DAC960-2.4.11.tar.gz)
    mv README.DAC960 linux/Documentation
    mv DAC960.[ch] linux/drivers/block
    patch -p0 < DAC960.patch (if DAC960.patch is included)
    cd linux
    make config
    make bzImage (or zImage)

  Then install "arch/x86/boot/bzImage" or "arch/x86/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 usable 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 all but
      one of them back online, after which a rebuild to the final drive is
      necessary.
  
      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.  The command
      should never be used on a dead drive that is part of a critical logical
      drive; rebuild should be used if only a single drive is dead.
  
    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