Allow percentage setting for size=

[fio.git] / HOWTO

diff --git a/HOWTO b/HOWTO
index 69b8cc6766850b6ceab07a0c15ea7e872142838e..ce1bd9e6131db987ea6c8992c5deeebd9bddc3bf 100644 (file)
--- a/HOWTO
+++ b/HOWTO
@@ -354,11 +354,19 @@ use_os_rand=bool Fio can either use the random generator supplied by the OS
                internal generator, which is often of better quality and
                faster.
 
-fallocate=bool By default, fio will use fallocate() to advise the system
-               of the size of the file we are going to write. This can be
-               turned off with fallocate=0. May not be available on all
-               supported platforms.  If using ZFS on Solaris this must be
-               set to 0 because ZFS doesn't support it.
+fallocate=str  Whether pre-allocation is performed when laying down files.
+               Accepted values are:
+
+                       none            Do not pre-allocate space
+                       posix           Pre-allocate via posix_fallocate()
+                       keep            Pre-allocate via fallocate() with
+                                       FALLOC_FL_KEEP_SIZE set
+                       0               Backward-compatible alias for 'none'
+                       1               Backward-compatible alias for 'posix'
+
+               May not be available on all supported platforms. 'keep' is only
+               available on Linux.If using ZFS on Solaris this must be set to
+               'none' because ZFS doesn't support it. Default: 'posix'.
 
 fadvise_hint=bool By default, fio will use fadvise() to advise the kernel
                on what IO patterns it is likely to issue. Sometimes you
@@ -374,7 +382,10 @@ size=int   The total size of file io for this job. Fio will run until
                fio will divide this size between the available files
                specified by the job. If not set, fio will use the full
                size of the given files or devices. If the the files
-               do not exist, size must be given.
+               do not exist, size must be given. It is also possible to
+               give size as a percentage between 1 and 100. If size=20%
+               is given, fio will use 20% of the full size of the given
+               files or devices.
 
 filesize=int   Individual file sizes. May be a range, in which case fio
                will select sizes for files at random within the given range