dt-usersguide.t

Linux磁盘测试的源代码,测试磁盘的读写性能

These options are used to specify various POSIX compliant open flags, and
system specific flags, to test the affect of these open modes.
.HS
Special Notes:
.bu
Each operating system has different flags, which can be queried by reviewing
the \fIdt\fP help text ("\fIdt help\fP").
.LP
.EX
    Syntax:
        flags=flags      Set open flags: {excl,sync,...}.
        oflags=flags     Set output flags: {append,trunc,...}.
.EE
.nh 2 On Child Error \&"\fIoncerr=\fP\&" Option.
This option allows you to control the action taken by \fIdt\fP when a
child process exits with an error.  By default, the action is \fIcontinue\fP,
which allows all child processes to run to completion.  If the child error
action is set to \fIabort\fP, then \fIdt\fP aborts all child processes
if \fBany\fP child process exits with an error status.
.EX
    Syntax:
        oncerr={abort|continue}  Set child error action.
.EE
.nh 2 Terminal Parity Setting \&"\fIparity=\fP\&" Option.
This option specifies the terminal parity setting to use during testing.
.EX
    Syntax:
        parity=string    Set parity to: even, odd, or none.
 on QNX parity=string    Set parity to: even, odd, mark, space, or none.
.EE
.nh 2 Pass Limit \&"\fIpasses=\fP\&" Option.
This option controls the number of passes to perform for each test.
.HS
Special Notes:
.bu
The default is to perform 1 pass.
.bu
When using the "\fIof=\fP" option, each write/read combination is
considered a single pass.
.bu
When multiple passes are specified, a different data pattern is used
for each pass, unless the user specified a data pattern or pattern file.
[ Please keep this in mind when using the "\fIdispose=keep\fP" option,
since using this same file for a subsequent \fIdt\fP read verify pass,
will report comparison errors... I've burned myself this way. ]
.LP
.EX
    Syntax:
        passes=value     The number of passes to perform.
.EE
.nh 2 Data Pattern \&"\fIpattern=\fP\&" Option.
This option specifies a 32 bit hexadecimal data pattern to be used for
the data pattern.  \fIdt\fP has 12 built-in patterns, which it alternates
through when running multiple passes.  The default data patterns are:
.EX 4
0x39c39c39, 0x00ff00ff, 0x0f0f0f0f, 0xc6dec6de, 0x6db6db6d, 0x00000000,
0xffffffff, 0xaaaaaaaa, 0x33333333, 0x26673333, 0x66673326, 0x71c7c71c
.EE
You can also specify the special keyword "\fIincr\fP" to use an incrementing
data pattern, or specify a character string (normally contained within single
or double quotes).
.EX
    Syntax:
        pattern=value    The 32 bit hex data pattern to use.
    or  pattern=iot      Use DJ's IOT test pattern.
    or  pattern=incr     Use an incrementing data pattern.
    or  pattern=string   The string to use for the data pattern.
.EE
So, what is DJ's IOT test pattern?  This pattern places the logical block
address (lba) in the first word (4 bytes) of each block, with (lba+=0x01010101)
being placed in all remaining words in the data block (512 bytes by default).
In this way, the logical block is seeded throughout each word in the block.
.PP
When specifying a pattern string via "\fIpattern=string\fP", the following
special mapping occors:
.EX
    Pattern String Mapping:
       \\\\ = Backslash   \\a = Alert (bell)   \\b = Backspace
       \\f = Formfeed    \\n = Newline        \\r = Carriage Return
       \\t = Tab         \\v = Vertical Tab   \\e or \\E = Escape
       \\ddd = Octal Value    \\xdd or \\Xdd = Hexadecimal Value

.EE
.nh 2 File Position \&"\fIposition=\fP\&" Option.
This option specifies a byte offset to seek to prior to starting each
pass of each test.
.EX
    Syntax:
        position=offset  Position to offset before testing.
.EE
.nh 2 Multiple Processes \&"\fIprocs=\fP\&" Option.
This option specifies the number of processes to initiate performing
the same test.  This option allows an easy method for initiating
multiple I/O requests to a single device or file system.
.HS
Special Notes:
.bu
The per process limit on Tru64 UNIX is 64, and can be queried by
using the "\fIsysconfig -q proc\fP" command.
.bu
Spawning many processes can render your system useless, well at least
very slow, and consumes large amounts of swap space (make sure you
have plenty!).
.bu
The parent process simply monitors (waits for) all child prcoesses.
.bu
When writing to a file system, the process ID (PID) is appending to
the file name specified with the "\fIof=\fP" option to create unique
file names.  If no pattern is specified, each process is started
with a unique data pattern.  Subsequent passes cycle through the
12 internal data patterns.  Use "\fIdisable=unique\fP" to avoid
this new (Version 14.1) behaviour.
.bu
The spawn() facility, used to execute on a different node, is not
implemented on the QNX Operating System at this time.
.LP
.EX
    Syntax:
        procs=value      The number of processes to create.
.EE
.nh 2 Random I/O Offset Alignment \&"\fIralign=\fP\&" Option.
This option is used when performing random I/O, to align each
random block offset to a particular alignment, for example 32K.
.LP
.EX
    Syntax:
        ralign=value     The random I/O offset alignment.
.EE
.nh 2 Random I/O Data Limit \&"\fIrlimit=\fP\&" Option.
This option is used with random I/O to specify the number of bytes
to limit random I/O between (starting from block 0 to this range).
This option is independent of the data limit option.
.LP
.EX
    Syntax:
        rlimit=value     The random I/O data byte limit.
.EE
.nh 2 Random Seed Value \&\fIrseed=\fP\&" Option.
This options sets the seed to initialize the random number generator
with, when doing random I/O.  When selecting random I/O, the total
statistics displays the random seed used during that test.  This
option can be used to repeat the random I/O sequence of a test.
.LP
.EX
    Syntax:
        rseed=value      The random seed to initialize with.
.EE
.nh 2 Record Limit \&"\fIrecords=\fP\&" Option.
This option controls the number of records to process for each write
and/or read pass of each test.  The "\fIcount=\fP" option is an alias
for this option (supported for \fIdd\fP compatibility).
.HS
Special Notes:
.bu
You must specify either a data limit, record limit, or files limit to
initiate a test, unless the device type is "disk", in which case \fIdt\fP
will automatically determine the disk capacity.
.bu
When specifying a runtime via the "\fIruntime=\fP" option, the record limit
controls how many records process for each pass (write and/or read pass).
.bu
If you specify a infinite "\fIrecords=Inf\fP" value, each pass will continue
until the end of media or file is reached.
.LP
.EX
    Syntax:
        records=value    The number of records to process.
.EE
.nh 2 Run Time \&"\fIruntime=\fP\&" Option.
This option controls how long the total test should run.  When used in
conjunction with a data limit or record limit, multiple passes will be
performed until the runtime limit expires.  A later section entitled
"\fITime Input Parameters\fP", describes the shorthand notation for
time values.
.EX
    Syntax:
        runtime=time     The number of seconds to execute.
.EE
.nh 2 Slices \&"\fIslices=\fP\&" Option.
This option is used with random access devices.  This option divides
the media into slices.  Each slice contains a different range of blocks
to operate on in a separate process.  If no pattern is specified, then
each slice is started with a unique data pattern.  Subsequent passes
alternate through \fIdt's\fP 12 internal patterns.
.EX
    Syntax:
        slices=value     The number of disk slices to test.
.EE
Note:  This option can be used in conjuntion with multiple processes
and/or asynchronous I/O options to generate a heavy I/O load, great
for stress testing!
.nh 2 Record Skip \&"\fIskip=\fP\&" Option.
This option specifies the numer of records to skip prior to starting
each write and/or read pass of each test.  The skips are accomplished
by reading records.
.EX
    Syntax:
        skip=value       The number of records to skip past.
.EE
.nh 2 Record Seek \&"\fIseek=\fP\&" Option.
This option specifies the number of records to seek past prior to
starting each write and/or read test.  The seeks are accomplished by
lseek()'ing past records, which is much faster than skipping when using
random access devices (\fIdd\fP could use this option).
.EX
    Syntax:
        seek=value       The number of records to seek past.
.EE
.nh 2 Data Step \&"\fIstep=\fP\&" Option.
This option is used to specify non-sequential I/O requests to random
access devices.  Normally, \fIdt\fP does sequential read & writes, but
this option specifies that step bytes be seeked past after each request.
.EX
    Syntax:
        step=value       The number of bytes seeked after I/O.
.EE
.nh 2 Terminal Speed \&"\fIspeed=\fP\&" Option.
This option specifies the terminal speed (baud rate) to setup prior to
initiating the test.  Although \fIdt\fP supports all valid baud rates, some
speeds may not be supported by all serial line drivers, and in some cases,
specifying higher speeds may result in hardware errors (e.g., silo overflow,
framing error, and/or hardware/software overrun errors).  The valid speeds
accepted by \fIdt\fP are:
.EX
         0        50        75       110       134       150
       200       300       600      1200      1800      2400
      4800      9600     19200     38400      57600   115200
.EE
Although a baud rate of zero is accepted, this is done mainly for testing
purposes (some systems use zero to hangup modems).  The higher baud rates
are only valid on systems which define the Bxxxxx speeds in termios.h.
.HS
Special Notes:
.bu
The default speed is 9600 baud.
.LP
.EX
    Syntax:
        speed=value      The tty speed (baud rate) to use.
.EE
.nh 2 Terminal Read Timeout \&"\fItimeout=\fP\&" Option.
This option specifies the timeout to use, in 10ths of a second, when
testing terminal line interfaces.  This is the timeout used between each
character after the first character is received, which may prevent tests
from hanging when a character is garbled and lost.
.HS
Special Notes:
.bu
The default terminal timeout is 3 seconds.
.bu
The default timeout is automatically adjusted for slow baud rates.
.LP
.EX
    Syntax:
        timeout=value    The tty read timeout in .10 seconds.
.EE
.nh 2 Terminal Read Minimum \&"\fIttymin=\fP\&" Option.
This option specifies the minmum number of characers to read, sets the
VMIN tty attribute.
.HS
Special Notes:
.bu
The tty VMIN field normally gets sets to the value of the block size
(\fIbs=balue\fP).
.bu
Note that on some systems, the VMIN field is an \fIunsigned char\fP,
so the maximum value is 255.
.bu
On QNX, this field is an \fIunsigned short\fP, so a maximum of 65535
is valid.
.LP
.EX
    Syntax:
        ttymin=value     The tty read minimum count (sets vmin).
.EE
.nh 2 Multiple Volumes \&"\fIvolumes=\fP\&" Option.
.nh 2 Multi-Volume Records \&"\fIvrecords=\fP\&" Option.
These options are used with removal media devices, to define how many
volumes and records on the last volume to process (i.e., tapes, etc).  
By using these options, you do not have to \fIguess\fP at a data limit
or record limit, to overflow onto subsequent volumes.  These options
automatically sets the "\fIenable=multi\fP" option. 
.EX
    Syntax:
        volumes=value    The number of volumes to process.
        vrecords=value   The record limit for the last volume.
.EE
.nh 2 Enable \&"\fIenable=\fP\&" & Disable "\fIdisable=\fP" Options.
These options are used to either enable or disable program flags which
either alter default test modes, test actions, or provide additional
debugging information.  You can specify a single flag or multiple flags
each seperated by a comma (e.g., "\fIenable=aio,debug,dump\fP").
.EX
    Syntax:
        enable=flag      Enable one or more of the flags below.
        disable=flag     Disable one or more of the flags below.
.EE
The flags which can be enabled or disabled are described below.
.nh 3 POSIX Asynchronous I/O \&"\fIaio\fP\&" Flag.
This flag is used to control use of POSIX Asynchronous I/O during testing,
rather than the synchronous I/O read() and write() system calls.
.HS
Special Notes:
.bu
This test mode is only supported on the Tru64 UNIX Operating System
at this time.