FreeBSD/Linux Kernel Cross Reference
sys/Documentation/README.DAC960

        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 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 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 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

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