dt-usersguide.t

Linux磁盘测试的源代码,测试磁盘的读写性能

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Beware, you may need to rebuild \fIdt\fP on new versions of Tru64 Unix
due to POSIX changes and/or AIO library changes between major releases.
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Reference the "\fIaios=\fP" option, for more special notes.
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    Flag:
        aio              POSIX Asynchronous I/O.(Default: disabled)
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.nh 3 Reporting Close Errors \&"\fIcerror\fP\&" Flag.
This flag controls where close errors are reported as an error or a
failure.  When disabled, close errors are reported as a warning.
This flag is meant to be used as a workaround for device drivers which
improperly return failures when closing the device.  Many system
utilities ignore close failures, but when testing terminals and
tapes, the close status us \fIvery\fP important.  For example with
tapes, the close reflects the status of writing filemarks (which
also flush buffered data), and the rewind status.
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    Flag:
        cerrors          Report close errors.   (Default: enabled)
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.nh 3 Data Comparison \&"\fIcompare\fP\&" Flag.
This flag disables data verification during the read pass of tests.
This flag should be disabled to read to end of file/media to obtain
maximum capacity statistics, or to obtain maximum performance statistics
(less overhead).
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    Flag:
        compare          Data comparison.       (Default: enabled)
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.nh 3 Core Dump on Errors \&"\fIcoredump\fP\&" Flag.
This flag controls whether a core file is generated, via abort(), when
\fIdt\fP is exiting with a failure status code.  This is mainly used for
program debug, and is not of much interest to normal users.  When testing
multiple processes, via fork(), this is the only way to debug since the
standard \fIdbx\fP debugger can't be used with child processes (this is
finally changing in the Tru64 UNIX V2.0 release, we've waited a long time).
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    Flag:
        coredump         Core dump on errors.   (Default: disabled)
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.nh 3 Diagnostic Logging \&"\fIdiag\fP\&" Flag.
This option is only valid on Tru64 Unix.  When enabled, error messages
get logged to the binary error logger.  This is useful to correlate
device error entries with test failures.  Please note, the logging
only occurs when running as superuser (API restriction, not mine!).
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    Flag:
        diag             Log diagnostic msgs.   (Default: disabled)
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.nh 3 Debug Output \&"\fIdebug\fP\&" Flag.
.nh 3 Verbose Debug Output \&"\fIDebug\fP\&" Flag.
.nh 3 Random I/O Debug Output \&"\fIrdebug\fP\&" Flag.
These flags enable two different levels of debug, which are useful when
trouble-shooting certain problems (i.e., what is \fIdt\fP doing to cause
this failure?).  Both flags can be specified for full debug output.
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    Flag:
        debug            Debug output.          (Default: disabled)
        Debug            Verbose debug output.  (Default: disabled)
        rdebug           Random debug output.   (Default: disabled)
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.nh 3 Dump Data Buffer \&"\fIdump\fP\&" Flag.
This flag controls dumping of the data buffer during data comparision failures.
If a pattern file is being used, then the pattern buffer is also dumped for
easy comparision purposes.  To prevent too many bytes from being dumped, esp.
when using large block sizes, dumping is limited to 64 bytes of data.
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Special Notes:
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When the failure occurs within the first 64 bytes of the buffer, dumping
starts at the beginning of the buffer.
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When the failure occurs at some offset within the data buffer, then dumping
starts at (data limit/2) bytes prior to the failing byte to provide context.
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The start of the failing data is marked by an asterisk '*'.
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You can use the \fIdlimit=\fP option to override the default dump limit.
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Buffer addresses are displayed for detection of memory boundary problems.
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    Flag:
        dump             Dump data buffer.      (Default: enabled)
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.nh 3 Tape EEI Reporting \&"\fIeei\fP\&" Flag.
This option controls the reporting of Extended Error Information (EEI)
on Tru64 UNIX systems, for tape devices when errors occur.  The standard
tape information available from \fImt\fP is reported, along with the EEI
status, CAM status, and SCSI request sense data.  This is excellent
information to help diagnose tape failures. (thank-you John Meneghini!)
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    Flag:
        eei              Tape EEI reporting.    (Default: enabled)
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.nh 3 Tape Reset Handling \&"\fIresets\fP\&" Flag.
This option is used during SCSI bus and device reset testing, to
reposition the tape position (tapes rewind on resets), and to
continue testing.  This option is only enabled for Tru64 UNIX
systems (currently), since this option requires reset detection
from EEI status, and tape position information from the CAM tape
driver (although \fIdt\fP also maintains the tape position as a
sanity check against the drivers' data).
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    Flag:
        resets           Tape reset handling.   (Default: disabled)
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.nh 3 Flush Terminal I/O Queues \&"\fIflush\fP\&" Flag.
This flag controls whether the terminal I/O queues get flushed before
each test begins.  This must be done to ensure no residual characters are
left in the queues from a prior test, or else data verification errors will
be reported.  Residual characters may also be left from a previous XOFF'ed
terminal state (output was suspended).
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    Flag:
        flush            Flush tty I/O queues.  (Default: enabled)
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.nh 3 Log File Header \&"\fIheader\fP\&" Flag.
When a log file is specified, \fIdt\fP automatically writes the command
line and \fIdt\fP version information at the beginning of the log file.
This option allows you to control whether this header should be written.
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    Flag:
        header           Log file header.       (Default: enabled)
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.nh 3 Logical Block Data Mode \&"\fIlbdata\fP\&" Flag.
This option enables a feature called logical block data mode.  This feature
allows reading/writing of a 4-byte (32-bit) logical block address at the
beginning of each data block tested.  The block number is stored using
SCSI byte ordering (big-endian), which matches what the SCSI Write Same
w/lbdata option uses, so \fIdt\fP can verify this pattern, generated
by \fIscu\fP's "write same" command.
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Special Notes:
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The starting logical block address defaults to 0, unless overridden with
the "\fIlba=\fP" option.
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The logical block size defaults to 512 bytes, unless overridden with
the "\fIlbs=\fP" option.
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The logical block address is always inserted started at the beginning of
each data block (record).
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Enabling this feature will degrade performance statistics (slightly).
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.nh 3 Enable Loopback Mode \&"\fIloopback\fP\&" Flag.
This flag specifies that either the input or output file should be used
in a loopback mode.  In loopback mode, \fIdt\fP forks(), and makes the
child process the reader, while the parent process becomes the writer.
In previous versions of \fIdt\fP, you had to specify both the same input
and output file to enable loopback mode.  When specifying this flag,
\fIdt\fP automatically duplicates the input or output device, which is
a little cleaner than the old method (which still works).
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Some people may argue that \fIdt\fP should automatically enable loopback
mode when a single terminal or FIFO device is detected.  The rationale
behind not doing this is described below:
.bn .
You may wish to have another process as reader and/or writer (which also
includes another program, not necessarily \fIdt\fP).
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You may wish to perform device loopback between two systems (e.g., to
verify the terminal drivers of two operating systems are compatible).
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A goal of \fIdt\fP is \fInot\fP to force (hardcode) actions or options
to make the program more flexible.  A minimum of validity checking is
done to avoid being too restrictive, although hooks exists to do this.
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Special Notes:
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The read verify flag is automatically disabled.
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This mode is most useful with terminal devices and/or FIFO's (named pipes).
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.nh 3 Microsecond Delays \&"\fImicrodelay\fP\&" Flag.
This flag tells \fIdt\fP that delay values, i.e. "\fIsdelay=\fP" and others,
should be executed using microsecond intervals, rather the second intervals.
(thank-you George Bittner for implementing this support!)
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    Flag:
        microdelay       Microsecond delays.    (Default: disabled)
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.nh 3 Memory Mapped I/O \&"\fImmap\fP\&" Flag.
This flag controls whether the memory mapped API is used for testing.
This test mode is currently supported on SUN/OS, Tru64 UNIX, and Linux
operating systems.
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Special Notes:
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The block size specified "\fIbs=\fP" \fImust\fP be a multiple of the system
dependent page size (normally 4k or 8k).
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An msync() is done after writing and prior to closing to force modified
pages to permanent storage.  It may be useful to add an option to inhibit
this action at some point, but my testing was specifically to time mmap
performance.  Obviously, invalidating the memory mapped pages, kind of
defeats the purpose of using memory mapped files in the first place.
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Specifying multiple passes when doing a read verify test, gives you a
good indication of the system paging utilization on successive passes.
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Memory mapping large data files (many megabytes) may exhaust certain
system resources.  On an early version of SUN/OS V4.0?, I could hang my
system by gobbling up all of physical memory and forcing paging (this
was certainly a bug which has probably been corrected since then).
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    Flag:
        mmap             Memory mapped I/O.     (Default: disabled)
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.nh 3 Test Modem Lines \&"\fImodem\fP\&" Flag.
This flag controls the testing of terminal modem lines.  Normally,
\fIdt\fP disables modem control, via setting CLOCAL, to prevent tests
from hanging.  When this flag is enabled, \fIdt\fP enables modem control,
via clearing CLOCAL, and then monitoring the modem signals looking for
either carrier detect (CD) or dataset ready (DSR) before allowing the
test to start.
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Special Notes:
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The program does not contain modem signal monitoring functions for the
all operating systems.  The functions in \fIdt\fP are specific to
Tru64 UNIX and ULTRIX systems, but these can be used as templates for
other operating systems.
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    Flag:
        modem            Test modem tty lines.  (Default: disabled)
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,nh 3 Multiple Volumes \&"\fImulti\fP\&" Flag.
This flag controls whether multiple volumes are used during testing.
When this flag is enabled, if the data limit or record count specified
does not fit on the current loaded media, the user is prompted to
insert the next media to continue testing.  Although this is used
mostly with tape devices, it can be used with any removeable media.
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    Flag:
        multi            Multiple volumes.      (Default: disabled)
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.nh 3 Control Per Pass Statistics \&"\fIpstats\fP\&" Flag.
This flag controls whether the per pass statistics are displayed.  If
this flag is disabled, a single summary line is still displayed per
pass and the total statistics are still displayed in the full format.
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    Flag:
        pstats           Per pass statistics.   (Default: enabled)
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.nh 3 Read After Write \&"\fIraw\fP\&" Flag.
This flag controls whether a read-after-write will be performed.
Sorry, \fIraw\fP does \fBnot\fP mean character device interface.
Normally \fIdt\fP performs a write pass, followed by a read pass.
When this flag is enabled the read/verify is done immediately after
the write.
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    Flag:
        raw              Read after write.      (Default: disabled)
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.nh 3 Control Program Statistics \&"\fIstats\fP\&" Flag.
This flag controls whether any statistics get displayed (both pass
and total statistics).  Disabling this flag also disabled the pass
statistics described above.
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    Flag:
        stats            Display statistics.    (Default: enabled)
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.nh 3 Table(sysinfo) timing \&"\fItable\fP\&" Flag.
On Tru64 UNIX systems, this option enables additional timing information
which gets reported as part of the statistics display. (thanks to
Jeff Detjen for adding this support!)
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    Flag:
        table            Table(sysinfo) timing. (Default: disabled)
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.nh 3 Unique Pattern \&"\fIunqiue\fP\&" Flag.
This flag controls whether multiple process, get a unqiue data
pattern.  This affects processes started with the "\fIslices=\fP"
or the "\fIprocs=\fP" options.  This only affects the \fIprocs=\fP
option when writing to a regular file.
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    Flag:
        unique           Unique pattern.        (Default: enabled)
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.nh 3 Verbose Output \&"\fIverbose\fP\&" Flag.
This flag controls certain informational program messages such as
reading and writing partial records.  If you find these messages
undesirable, then they can be turned off by disabling this flag.
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    Flag:
        verbose          Verbose output.        (Default: enabled)
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.nh 3 Verify Data \&"\fIverify\fP\&" Flag.
This flag controls whether the read verify pass is performed automatically
after the write pass.  Ordinarily, when specifying an output device via
the "\fIof=\fP" option, a read verify pass is done to read and perform a
data comparision.  If you only wish to write the data, and omit the data
verification read pass, then disable this flag.
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    Flag:
        verify           Verify data written.    (Default: enabled)
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