Provided by: scsitools_0.12-3ubuntu1_amd64 bug

NAME

       scsi-config - query information from a scsi device with a nice user interface

SYNOPSIS

       scsi-config [device]

DESCRIPTION

       scsi-config  queries  information  from  an  scsi target with a nice Tcl/Tk user interface. If you do not
       specify a device to query, scsi-config calculates a list of available devices and prompts it to you.

       By the nature of a graphical user interface, most things will explain them self.  Basically,  scsi-config
       shows a list of buttons for certain mode pages which you may press. Those buttons which you can press and
       the text windows with white backgrounds can be modified by you and the modifications  send  back  to  the
       device.

       In  the main window there is a button to instruct the device to save the data in some non volatile memory
       (if it supports it). Note that this will instruct the device to save the Read-Write Error Recovery Page ,
       Disconnect-Reconnect  Page  ,  Format  Device  Page  , Caching Page , and Control Mode Page in its NVRAM.
       Usually saving even a single of those should write them all to the NVRAM, but you never know.

       You can query the current, the factory default and the values in the NVRAM (which may not be the  current
       parameters) from the device.

       Not all combinations of button toggles or all values are valid. In general, try to set them and see which
       values the drive accepts.  scsi-config rereads the device configuration immediately, s.t. you  see  which
       values where accepted.

       Also  note  that  some  disk  drives  are notched, and that those have an active notch (shown in the main
       window) to which all your settings apply (at least those of notched pages, which are also marked in slate
       gray).  You  can  select the active notch to which your settings apply (and to which the values refer) in
       the Notch Page.

       For those devices which do not feature an NVRAM (generally removable media devices)  and  as  a  kind  of
       backup,  you  can  save the current settings to a file. Actually the file will be a /bin/sh script making
       the necessary scsiinfo(8) calls to set the saved parameters when executed.

       There is also a nice Overview button which will query many details about the disk geometry and draw  them
       in  a  nice  picture. This looks esp. nice for drives with many notches, that is different regions on the
       disk with different tracks per sector settings. It is also very useful for  notched  drives  as  you  can
       immediately select the mode pages for each notch.

SOME USAGE GUIDELINES

       1. General Warning
              Generally,  do  not  modify  settings you don't understand. It is useful to know the SCSI-II specs
              mentioned below. Some setting may render the device unusable or even damage it.  Usually  a  power
              cycle  resets  the  state  (if  you  do  not  save the weird settings in the NVRAM). Some settings
              affecting the assignment of logical sectors will render the disk unusable until the next low level
              format.

       2. On Write Caching
              As  an  old  warning,  this does also mean you should not generally switch the write cache on.  At
              least on those drives where you have a choice at all. Reasons are twofold:

              a)     It is a priori unclear when the drive will actually perform the writes. This is a bad thing
                     when  considering  shutdown of your machine. On the other hand, it seems sensible to assume
                     that the drive will immediately write it's cache to disk when it is idle  (after  all  file
                     systems are unmounted) and due to the size of the on disk cache this will usually only need
                     a few seconds after the shutdown (but the drive lamp will usually not glow, as it is mostly
                     connected to the host adapter (if you have a lamp at all) and it is not participating).

                     There  is  a  SCSI command to flush the caches. Linux could call it prior to shutting down,
                     spinning a disk down. Due to my knowledge this is not yet done though.

              b)     As the writes are performed asynchronously, errors are reported  asynchronously.  The  disk
                     might  return  an  error  at  some  simple  read  instruction  related to a write which was
                     acknowledged OK  several  transactions  ago.  This  generally  confuses  things  and  makes
                     interpreting  errors very difficult. Some devices are known/said to not report write errors
                     in this mode of operation at all.

                     Just imagine that at the point where a file system is unmounted, or a new  removable  media
                     is detected it could tell: Oops, BTW, there was some write error ago although I told you it
                     was OK already.

              Thus, when you run a disk in write cache mode, keep it in mind when weird error messages occur and
              give  the disk time to flush it's buffers at shutdown. Generally it would be good if you knew more
              vendor specific details on how the disk operates in the write cache mode.

       3. Reassigning Bad Blocks Automatically
              One of the nice features of SCSI disk is that they allow to remap bad blocks automatically as they
              are detected without any user intervention. However, you actually have to enable this feature!  It
              turned out that you can not generally assume a disk in this mode. To enable this mode or check the
              settings, proceed as follows:

              a)     Go  to  the Read-Write Error Recovery Page.  AWRE (Automatic Write Reallocation Enable) and
                     ARRE (Automatic Read Reallocation Enable) buttons enable the automatic reallocation.

                     In the same window, you can select the maximal retries performed. EER allows the disk to do
                     some  Early  Error  Recovery  which  is  fast  (but might misdetect or miscorrect data).  A
                     selected DCR button (Disable  CoRrection  Codes)  disallows  the  disk  to  use  any  error
                     correction  codes at all (thus the drive will have to retry until it performs an error free
                     read).

                     Usually a sector will be reallocated after even a single read retry or the given number  of
                     failed  write  retries. When the sector cannot be recovered, it is reallocated but the data
                     is lost and an error is signalled.

                     The other buttons there apply to error reporting  as  well.  TB  Transmits  the  bad  Block
                     together  with  the  error,  RC  Reads Continuous, that is, does not pause a read operation
                     while retrying or using error code calculations to recover a bad block (thus may return bad
                     data).  PER  lets the disk report even recovered errors (Post ERror), DTE (Disable Transfer
                     on Error) even breaks a running data transmission when an error is detected.

              b)     Even when the reallocation is enabled, the disk must  actually  have  some  reserved  areas
                     where  to  remap  the  bad  blocks. The Format Page controls this. Either a given number of
                     Alternate Sectors Per LUN is set aside for the whole disk or a given number  of  tracks  is
                     defined  to  be a zone and for each zone a number of sectors or tracks is put aside.  These
                     alternate data areas are where bad sectors are remapped.

                     Note that this page is very likely to apply only to the current notch  on  a  notched  disk
                     device.

                     If there are no, or not many alternate sectors reserved on your disk, you must change these
                     settings.

                     I found that those disks which allow to modify these settings are  very  often  set  to  no
                     reserved  sectors at all by the vendors, as this increases the disks capacity. For the sake
                     of stability, you should really modify these settings.

                     If you decide to modify the number of alternate sectors, you must

                     i)     Save the parameters to the NVRAM of the disk.

                     ii)    Low-level format the disk drive (and not erase the NVRAM during this operation).

                     to make the changes be effective.

              c)     Esp. when you set the disk to not report recovered errors (or when it is in a  write  cache
                     mode  or something), and just as a general guideline, keep an eye on the grown defects list
                     where the disk will report all the remappings which took place as your disk ages.

                     The old adventurers guide line applies: Save (Backup) Early, Save (Backup) Often. Find  the
                     right time to replace your disk avoiding too much work recovering your data.

BUGS

       scsi-config  could  be enhanced by making better use of Tcl/Tk. I learned much about it during my work on
       tk_scsiformat(8) and their would be much room for fixes and enhances. On  other  hand,  it  fulfils  it's
       purpose as it is quite nicely already.

       As scsi-config makes heavy use of scsiinfo(8) all it's bugs (esp. on defect reading) apply.

FILES

       /usr/lib/scsi/cache,      /usr/lib/scsi/control,      /usr/lib/scsi/disconnect,      /usr/lib/scsi/error,
       /usr/lib/scsi/format,      /usr/lib/scsi/generic,       /usr/lib/scsi/inquiry,       /usr/lib/scsi/notch,
       /usr/lib/scsi/overview,    /usr/lib/scsi/peripheral,   /usr/lib/scsi/rigid,   /usr/lib/scsi/save-changes,
       /usr/lib/scsi/save-file, /usr/lib/scsi/tworands, /usr/lib/scsi/verify (Tcl/Tk subroutines used  by  scsi-
       config).
       /dev/sd*
       /dev/sg*
       /dev/scd*
       /dev/st*
       /dev/nst*
       /dev/rmt*
       /dev/nrmt*

SEE ALSO

       scsiinfo(8), scsiformat(8), tk_scsiformat(8), fdisk(8), sd(4),

       Draft proposed
       American National Standard
       for information systems

       SMALL COMPUTER SYSTEM INTERFACE - 2
       (SCSI-2)

       MARCH 9, 1990

AUTHORS

       Eric Youngdale.
       Michael Weller <eowmob@exp-math.uni-essen.de>, Versions 1.5 & 1.7