Fio 1.52

[fio.git] / HOWTO

diff --git a/HOWTO b/HOWTO
index 68e17e9f4743b6738fe10c1e329be9783f8af746..69b8cc6766850b6ceab07a0c15ea7e872142838e 100644 (file)
--- a/HOWTO
+++ b/HOWTO
@@ -348,6 +348,12 @@ kb_base=int        The base unit for a kilobyte. The defacto base is 2^10, 1024.
 randrepeat=bool        For random IO workloads, seed the generator in a predictable
                way so that results are repeatable across repetitions.
 
+use_os_rand=bool Fio can either use the random generator supplied by the OS
+               to generator random offsets, or it can use it's own internal
+               generator (based on Tausworthe). Default is to use the
+               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
@@ -375,10 +381,15 @@ filesize=int      Individual file sizes. May be a range, in which case fio
                and limited to 'size' in total (if that is given). If not
                given, each created file is the same size.
 
-fill_device=bool Sets size to something really large and waits for ENOSPC (no
+fill_device=bool
+fill_fs=bool   Sets size to something really large and waits for ENOSPC (no
                space left on device) as the terminating condition. Only makes
                 sense with sequential write. For a read workload, the mount
-               point will be filled first then IO started on the result.
+               point will be filled first then IO started on the result. This
+               option doesn't make sense if operating on a raw device node,
+               since the size of that is already known by the file system.
+               Additionally, writing beyond end-of-device will not return
+               ENOSPC there.
 
 blocksize=int
 bs=int         The block size used for the io units. Defaults to 4k. Values