Add support for non-uniformly random file service type

[fio.git] / HOWTO

diff --git a/HOWTO b/HOWTO
index 88d10a171da9e373ee40e5844b2b1690c6b3db28..9ed2c5f5580365c69664eecb651f7e1b4065df7b 100644 (file)
--- a/HOWTO
+++ b/HOWTO
@@ -673,10 +673,23 @@ file_service_type=str  Defines how fio decides which file from a job to
                                the next. Multiple files can still be
                                open depending on 'openfiles'.
 
-               The string can have a number appended, indicating how
-               often to switch to a new file. So if option random:4 is
-               given, fio will switch to a new random file after 4 ios
-               have been issued.
+                       zipf    Use a zipfian distribution to decide what file
+                               to access.
+
+                       pareto  Use a pareto distribution to decide what file
+                               to access.
+
+                       gauss   Use a gaussian (normal) distribution to decide
+                               what file to access.
+
+               For random, roundrobin, and sequential, a postfix can be
+               appended to tell fio how many I/Os to issue before switching
+               to a new file. For example, specifying
+               'file_service_type=random:8' would cause fio to issue 8 I/Os
+               before selecting a new file at random. For the non-uniform
+               distributions, a floating point postfix can be given to
+               influence how the distribution is skewed. See
+               'random_distribution' for a description of how that would work.
 
 ioengine=str   Defines how the job issues io to the file. The following
                types are defined: