Add string support for buffer_pattern

[fio.git] / HOWTO

diff --git a/HOWTO b/HOWTO
index d7283535db0d8ddff7908422185fe5cdb9480b76..73e58ff695c3384df30094d6c15ebe9ed615460f 100644 (file)
--- a/HOWTO
+++ b/HOWTO
@@ -569,6 +569,8 @@ buffer_pattern=str  If set, fio will fill the io buffers with this pattern.
                If not set, the contents of io buffers is defined by the other
                options related to buffer contents. The setting can be any
                pattern of bytes, and can be prefixed with 0x for hex values.
+               It may also be a string, where the string must then be
+               wrapped with "".
 
 nrfiles=int    Number of files to use for this job. Defaults to 1.
 
@@ -694,7 +696,21 @@ ioengine=str       Defines how the job issues io to the file. The following
                                having to go through FUSE. This ioengine
                                defines engine specific options.
 
-                       hdfs    Read and write through Hadoop (HDFS).
+                       libhdfs Read and write through Hadoop (HDFS).
+                               The 'filename' option is used to specify host,
+                               port of the hdfs name-node to connect. This
+                               engine interprets offsets a little
+                               differently. In HDFS, files once created
+                               cannot be modified. So random writes are not
+                               possible. To imitate this, libhdfs engine
+                               expects bunch of small files to be created
+                               over HDFS, and engine will randomly pick a
+                               file out of those files based on the offset
+                               generated by fio backend. (see the example
+                               job file to create such files, use rw=write
+                               option). Please note, you might want to set
+                               necessary environment variables to work with
+                               hdfs/libhdfs properly.
 
                        external Prefix to specify loading an external
                                IO engine object file. Append the engine