dt-usersguide.txt

Linux磁盘测试的源代码,测试磁盘的读写性能

                                    User's Manual

                                         for

                               dt - Data Test Program
                                    Version 13.22

                                         by
                                   Robin T. Miller
                                 November 10th, 2000







              _______________________________________________________
                                 EXTREME WARNING!!!
                  Use of this program is almost guaranteed to find
                 problems and cause your schedules to slip.  If you
               are afraid to find bugs or otherwise break your system,
                  then please do not use this program for testing.
                You can pay now or pay later, but you've been warned.
              _______________________________________________________




                    The Author of dt,
                    Robin's Nest Software Inc.      Home e-mail: [e-mail]
                    Robin T. Miller         or      Work e-mail: [e-mail]
                    2 Paradise Lane,                QUICS Login: rtmiller
                    Hudson, N.H. 03051
                    Home: [phone]            Work: [phone]


          Users Manual for                              November 10th, 2000
          dt - Data Test Program                              Version 13.22


                                   Change History



          Version          Date               Author                        Changes
          __________________________________________________________________________________________
           13.22    November 10th, 2000   Robin T. Miller

                                                            Added more test  features  and  options,
                                                            including:  read-after-write (raw), set-
                                                            ting the random I/O  seed  (rseed),  and
                                                            multi-volume media testing.
          __________________________________________________________________________________________
           12.0     July 24, 1999         Robin T. Miller

                                                            Add  numerous  new  test  features   and
                                                            parameters, including: AIO w/lbdata, AIO
                                                            w/random, EEI & tape  resets,  IOT  test
                                                            pattern,  larger  data/record limits and
                                                            statistics, Linux & Windows/NT support.
          __________________________________________________________________________________________
            9.3     February 21, 1996     Robin T. Miller

                                                            Documented iotype={random or sequential}
                                                            option.
          __________________________________________________________________________________________
            9.0     December 11, 1995     Robin T. Miller

                                                            Logical block data  feature,  additional
                                                            (higher)  tty  speeds,  and  other minor
                                                            changes.
          __________________________________________________________________________________________
            8.0     July 26, 1995         Robin T. Miller

                                                            Modem testing,  child  process  control,
                                                            pattern  string  enhancements, and other
                                                            minor changes.
          __________________________________________________________________________________________
            7.0     September 11, 1993    Robin T. Miller   Initial release of Users Manual.
          __________________________________________________________________________________________


          Users Manual for                              November 10th, 2000
          dt - Data Test Program                              Version 13.22



          1  Overview.

               dt is a generic data test program used to verify the  proper
          operation  of  peripherals  &  I/O sub-systems, and for obtaining
          performance information.  Since  verification  of  data  is  per-
          formed, dt can be thought of as a generic diagnostic tool.

               Although the original design goals of being a  generic  test
          tool  were  accomplished,  it  quickly become evident that device
          specific tests, such  as  terminals,  and  different  programming
          interfaces such as memory mapped files and POSIX asynchronous I/O
          API's were necessary.  Therefore, special options were  added  to
          enable these test modes and to specify necessary test parameters.

               dt command lines are similar to the  dd  program,  which  is
          popular  on  most  UNIX systems.  dt contains numerous options to
          provide user control of most test parameters so customized  tests
          can  be  written  easily and quickly by specifying simple command
          line options.  Since  the  exit  status  of  the  program  always
          reflects  the  completion  status  of  a test, scripts can easily
          detect failures to perform automatic regression tests.

               dt has been used to successfully test disks,  tapes,  serial
          lines,  parallel  lines, pipes & FIFO's, memory mapped files, and
          POSIX Asynchronous I/O.  In fact, dt can be used with any  device
          that  supports  the  standard open, read, write, and close system
          calls.  Special support is necessary for some  devices,  such  as
          serial  lines,  for setting up the speed, parity, data bits, etc,
          but dt's design provides easy addition of this setup.

               Most tests can be initiated by a simple dt command line, and
          lots  of  I/O  can  be initiated quickly using multiple processes
          and/or POSIX AIO, for  those  operating  systems  supporing  AIO.
          More  complex  tests  are  normally  initiated  by  writing shell
          scripts and using dt in conjunction with other tools, such as scu
          (SCSI Command Utility).  Several shell scripts for testing disks,
          tapes, and serial lines are also supplied with this kit which can
          used as templates for developing other specialized test scripts.

               Specific system features are now being added to dt  so  more
          extensive testing can be accomplished.  The program has been res-
          tructured to allow easy inclusion of new device specific tests by
          dispatching  to  test  functions through a function lookup table.
          This table gets setup automatically  by  the  program,  based  on
          options enabled, or via the device type "dtype=" option.









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          Users Manual for                              November 10th, 2000
          dt - Data Test Program                              Version 13.22




           WARNING: dt does NOT perform any sanity checking  of  the  output
           device  specified.   This  means if you are running as 'root' and
           you specify a raw disk device, dt will  overwrite  existing  file
           systems, so please be careful.

           NOTE: Tru64 (Digital) UNIX prevents overwriting  the  disk  label
           block (block 0), to prevent you from destroying this valuable in-
           formation.  Overwriting other  files  systems,  not  starting  at
           block zero, is still possible however.


          2  Operating Systems Supported.


               dt is conditionalized to  run  on  SUN,  ULTRIX,  OSF,  QNX,
          Windows/NT, and Linux operating systems.  This conditionalization
          tends to make the source look rather  ugly,  but  I've  purposely
          left  this in for code maintainability (common code base) and for
          other people to see porting differences  between  these  systems.
          UNIX is NOT as portable as some people think, but the POSIX stan-
          dard is finally changing this.  Eventually this will  be  cleaned
          up,  but  this conditionization is currently necessary so dt will
          compile and run with non-ANSI compliant compilers  and  non-POSIX
          compliant operating systems.

          2.1  POSIX Compliant Systems.

               People who may wish to port  dt  to  other  POSIX  compliant
          operating  systems,  should review the Tru64 UNIX, Linux, and QNX
          conditionalized code.  These operating systems  also  support  an
          ANSI compliant compiler.


          3  Test Uses.

               Those poeple with an imagination will find many uses for dt,
          but I'll list a few I've used it for, just to whet your appetite:
            o  Testing of tape  devices  using  different  block  sizes  to
               determine  the  best blocking factor for optimum performance
               and capacity.  This is very important  for  streaming  tapes
               devices.
            o  Write tapes to end of tape,  to  determine  the  total  tape
               capacity.   This  gives  the  total  data capacity of tapes,
               after inter-record gaps, preamble/postambles, or pad  blocks
               are written on the tape.
            o  Read existing tapes with data comparison disabled, to deter-
               mine  the  amount  of  data  on the tape.  This is useful to
               determine how much disk space is required to read in a tape,
               or to simply verify the tape can be read without errors.




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          dt - Data Test Program                              Version 13.22



            o  Reading/writing an entire  tape  to  ensure  device  drivers
               properly sense and handle end of tape error conditions.
            o  Write a tape and ensure it can be read on another tape drive
               to test drive compatibility (also referred to as transporta-
               bility).
            o  Read multiple tape files to ensure file  marks  and  end  of
               tape are reported and handled properly by tape drivers.
            o  I/O to disks using the raw device  interface,  to  determine
               the  optimum  performance  of  the controller.  This usually
               gives a good indication of how well the controller cache  or
               read-ahead improves I/O performance for sequential or random
               file access.
            o  I/O to disk files through the file system, to determine  the
               affect  the  buffer cache has on write and read performance.
               You must know the characteristics of your O/S's buffer cache
               to  select file sizes to either get optimum performance from
               the cache, or to defeat the affect of the buffer cache.
            o  Reading/writing of entire disks, to ensure the  media  capa-
               city and end of media error handling is properly reported by
               device drivers.
            o  Test memory mapped files to compare I/O performance  against
               raw  and  file  system  I/O.   Typically,  memory mapped I/O
               approaches the raw device performance.
            o  Testing I/O to files on NFS mounted file systems.  This will
               give  you  a good indication of your ethernet performance to
               remote files.
            o  Writing/reading pipes & FIFO's to verify pipe operation  and
               performance.
            o  Initiating  multiple  processes  to  test  optimizations  of
               buffer  cache,  device drivers, and/or intelligent controll-
               ers.  This is also useful to test multiple device access and
               for loading the I/O sub-system.
            o  Force I/O at different memory boundaries to test  low  level
               driver handling.  Using the align option, you can set memory
               alignment for testing specialized device  driver  DMA  code.
               This is very useful when developing new I/O sub-systems.
            o  Do loopback testing of parallel or serial  lines  on  either
               the same system of different systems.  This is a useful com-
               patibility test when running different machines running dif-
               ferent operating systems.
            o  Enable POSIX Asynchronous I/O to verify proper operation  of
               this  API  and to determine performance gains (over standard
               synchronous I/O).  This is also useful for queuing  multiple
               I/O requests to drivers and for testing SCSI tag queuing and
               RAID configurations.
            o  Specify variable record options for  testing  variable  tape
               devices.
            o  On Tru64 cluster systems,  distributed  lock  manager  (DLM)
               options  can  be used to control access to shared devices or
               files.




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          Users Manual for                              November 10th, 2000
          dt - Data Test Program                              Version 13.22



            o  Also available on Tru64 UNIX is the ability to use  Extended
               Error  Information  (EEI)  to  detect  and recover from SCSI
               bus/device resets (tape is repositioned for  continuing  the
               test).



          4  Program Options.

               This section describes program options and and special notes
          related  to  each.   The  dt  help file provides a summary of the
          options, and the default value of most options.  The dt help sum-
          mary for Tru64 UNIX is shown in Appendix A.

          4.1  Input File "if=" Option.

               This option specifies the input file to open for reads.  The
          device  is  opened read-only so devices which only permit or sup-
          port read access, e.g., parallel input  devices,  can  be  opened
          successfully.

          Special Notes:
            o  Data read is automatically verified with  the  default  data
               pattern,   unless   you   disable   this   action   via  the
               "disable=compare" option.
            o  Extra pad bytes of sizeof(int), are allocated at the end  of
               data  buffers,  initialized  with the inverted data pattern,
               and then verified after each read request to ensure the  end
               of data buffers didn't get overwritten by file system and/or
               device drivers.  This extra check has  found  problems  with
               flushing DMA FIFO's on several machines.


              Syntax:
                  if=filename      The input file to read.


          4.2  Output File "of=" Option.

               This option specifies the output file to  open  for  writes.
          After  the  write  portion  of the test, the device is closed (to
          reposition to start of file or to rewind  the  tape),  re-opened,