Add randtrimwrite data direction

[fio.git] / HOWTO.rst

diff --git a/HOWTO.rst b/HOWTO.rst
index c94238ed5b84733945cd441a70526d5b9b1c778c..e89d05f04791d22d9369aa9466b48d5e86dfc1ab 100644 (file)
--- a/HOWTO.rst
+++ b/HOWTO.rst
@@ -167,9 +167,9 @@ Command line options
        defined by `ioengine`.  If no `ioengine` is given, list all
        available ioengines.
 
        defined by `ioengine`.  If no `ioengine` is given, list all
        available ioengines.
 

-.. option:: --showcmd=jobfile
+.. option:: --showcmd

 
 

-       Convert `jobfile` to a set of command-line options.
+       Convert given job files to a set of command-line options.

 
 .. option:: --readonly
 
 
 .. option:: --readonly
 


@@ -1129,7 +1129,14 @@ I/O type
                                Random mixed reads and writes.
                **trimwrite**
                                Sequential trim+write sequences. Blocks will be trimmed first,
                                Random mixed reads and writes.
                **trimwrite**
                                Sequential trim+write sequences. Blocks will be trimmed first,

-                               then the same blocks will be written to.
+                               then the same blocks will be written to. So if ``io_size=64K``
+                               is specified, Fio will trim a total of 64K bytes and also
+                               write 64K bytes on the same trimmed blocks. This behaviour
+                               will be consistent with ``number_ios`` or other Fio options
+                               limiting the total bytes or number of I/O's.
+               **randtrimwrite**
+                               Like trimwrite, but uses random offsets rather
+                               than sequential writes.

 
        Fio defaults to read if the option is not specified.  For the mixed I/O
        types, the default is to split them 50/50.  For certain types of I/O the
 
        Fio defaults to read if the option is not specified.  For the mixed I/O
        types, the default is to split them 50/50.  For certain types of I/O the


@@ -2550,7 +2557,7 @@ with the caveat that when used on the command line, they must come after the
 
    [dfs]
 
 
    [dfs]
 

-       Specificy a different chunk size (in bytes) for the dfs file.
+       Specify a different chunk size (in bytes) for the dfs file.

        Use DAOS container's chunk size by default.
 
    [libhdfs]
        Use DAOS container's chunk size by default.
 
    [libhdfs]


@@ -2559,7 +2566,7 @@ with the caveat that when used on the command line, they must come after the
 
 .. option:: object_class=str : [dfs]
 
 
 .. option:: object_class=str : [dfs]
 

-       Specificy a different object class for the dfs file.
+       Specify a different object class for the dfs file.

        Use DAOS container's object class by default.
 
 .. option:: skip_bad=bool : [mtd]
        Use DAOS container's object class by default.
 
 .. option:: skip_bad=bool : [mtd]


@@ -3927,6 +3934,13 @@ Error handling
        appended, the total error count and the first error. The error field given
        in the stats is the first error that was hit during the run.
 
        appended, the total error count and the first error. The error field given
        in the stats is the first error that was hit during the run.
 

+       Note: a write error from the device may go unnoticed by fio when using
+       buffered IO, as the write() (or similar) system call merely dirties the
+       kernel pages, unless :option:`sync` or :option:`direct` is used. Device IO
+       errors occur when the dirty data is actually written out to disk. If fully
+       sync writes aren't desirable, :option:`fsync` or :option:`fdatasync` can be
+       used as well. This is specific to writes, as reads are always synchronous.
+

        The allowed values are:
 
                **none**
        The allowed values are:
 
                **none**