Add offset_align option

[fio.git] / HOWTO

diff --git a/HOWTO b/HOWTO
index 22a58496921ba229db6a413696595aaa014d5ca9..e7142c57b03df0e6f500b35ad95cf712d4c20617 100644 (file)
--- a/HOWTO
+++ b/HOWTO
@@ -1128,13 +1128,20 @@ I/O type
 .. option:: offset=int
 
        Start I/O at the provided offset in the file, given as either a fixed size in
-       bytes or a percentage. If a percentage is given, the next ``blockalign``-ed
-       offset will be used. Data before the given offset will not be touched. This
+       bytes or a percentage. If a percentage is given, the generated offset will be
+       aligned to the minimum ``blocksize`` or to the value of ``offset_align`` if
+       provided. Data before the given offset will not be touched. This
        effectively caps the file size at `real_size - offset`. Can be combined with
        :option:`size` to constrain the start and end range of the I/O workload.
        A percentage can be specified by a number between 1 and 100 followed by '%',
        for example, ``offset=20%`` to specify 20%.
 
+.. option:: offset_align=int
+
+       If set to non-zero value, the byte offset generated by a percentage ``offset``
+       is aligned upwards to this value. Defaults to 0 meaning that a percentage
+       offset is aligned to the minimum block size.
+
 .. option:: offset_increment=int
 
        If this is provided, then the real offset becomes `offset + offset_increment