Basic support for dedupe

[fio.git] / HOWTO

diff --git a/HOWTO b/HOWTO
index d7283535db0d8ddff7908422185fe5cdb9480b76..23746cec199e05c6a34ed007794f5c45abc6e8e5 100644 (file)
--- a/HOWTO
+++ b/HOWTO
@@ -565,10 +565,20 @@ buffer_compress_chunk=int See buffer_compress_percentage. This
                alternate random and zeroed data throughout the IO
                buffer.
 
-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.
+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 "".
+
+dedupe_percentage=int  If set, fio will generate this percentage of
+               identical buffers when writing. These buffers will be
+               naturally dedupable. The contents of the buffers depend on
+               what other buffer compression settings have been set. It's
+               possible to have the individual buffers either fully
+               compressible, or not at all. This option only controls the
+               distribution of unique buffers.
 
 nrfiles=int    Number of files to use for this job. Defaults to 1.
 
@@ -694,7 +704,21 @@ 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