Warn more gently if the kernel is too old for io scheduler switching

[fio.git] / HOWTO

diff --git a/HOWTO b/HOWTO
index 8312d9315ae3a591b7a85cdd0822c86626ace840..7cab05379f612034abdc173f03acb8d7850f902f 100644 (file)
--- a/HOWTO
+++ b/HOWTO
@@ -555,10 +555,22 @@ verify=str        If writing to a file, fio can verify the file contents
                        crc32   Use a crc32 sum of the data area and store
                                it in the header of each block.
 
                        crc32   Use a crc32 sum of the data area and store
                                it in the header of each block.
 

+                       null    Only pretend to verify. Useful for testing
+                               internals with ioengine=null, not for much
+                               else.
+

                This option can be used for repeated burn-in tests of a
                system to make sure that the written data is also
                correctly read back.
 
                This option can be used for repeated burn-in tests of a
                system to make sure that the written data is also
                correctly read back.
 

+verifysort=bool        If set, fio will sort written verify blocks when it deems
+               it faster to read them back in a sorted manner. This is
+               often the case when overwriting an existing file, since
+               the blocks are already laid out in the file system. You
+               can ignore this option unless doing huge amounts of really
+               fast IO where the red-black tree sorting CPU time becomes
+               significant.
+               

 stonewall      Wait for preceeding jobs in the job file to exit, before
                starting this one. Can be used to insert serialization
                points in the job file. A stone wall also implies starting
 stonewall      Wait for preceeding jobs in the job file to exit, before
                starting this one. Can be used to insert serialization
                points in the job file. A stone wall also implies starting