Don't truncate files if we don't need to extend them

[fio.git] / HOWTO

diff --git a/HOWTO b/HOWTO
index d5fb52cfb0f9f931db588c78d92e81a95480f2ca..7b717f7739664f44393d67b7b6521e8ca0404eae 100644 (file)
--- a/HOWTO
+++ b/HOWTO
@@ -262,6 +262,10 @@ filesize=siint     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.
 
                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
+               space left on device) as the terminating condition. Only makes
+                sense with sequential write.
+

 blocksize=siint
 bs=siint       The block size used for the io units. Defaults to 4k. Values
                can be given for both read and writes. If a single siint is
 blocksize=siint
 bs=siint       The block size used for the io units. Defaults to 4k. Values
                can be given for both read and writes. If a single siint is


@@ -281,6 +285,30 @@ bsrange=irange     Instead of giving a single block size, specify a range
                writes, however a second range can be given after a comma.
                See bs=.
 
                writes, however a second range can be given after a comma.
                See bs=.
 

+bssplit=str    Sometimes you want even finer grained control of the
+               block sizes issued, not just an even split between them.
+               This option allows you to weight various block sizes,
+               so that you are able to define a specific amount of
+               block sizes issued. The format for this option is:
+
+                       bssplit=blocksize/percentage:blocksize/percentage
+
+               for as many block sizes as needed. So if you want to define
+               a workload that has 50% 64k blocks, 10% 4k blocks, and
+               40% 32k blocks, you would write:
+
+                       bssplit=4k/10:64k/50:32k/40
+
+               Ordering does not matter. If the percentage is left blank,
+               fio will fill in the remaining values evenly. So a bssplit
+               option like this one:
+
+                       bssplit=4k/50:1k/:32k/
+
+               would have 50% 4k ios, and 25% 1k and 32k ios. The percentages
+               always add up to 100, if bssplit is given a range that adds
+               up to more, it will error out.
+

 blocksize_unaligned
 bs_unaligned   If this option is given, any byte size value within bsrange
                may be used as a block range. This typically wont work with
 blocksize_unaligned
 bs_unaligned   If this option is given, any byte size value within bsrange
                may be used as a block range. This typically wont work with