HOWTO: Mention fsync=/fsyncdata= are set to 0 by default

[fio.git] / HOWTO

diff --git a/HOWTO b/HOWTO
index c2c65096bbd22461590c502aba6771b26598f672..cae95b7720f210893bb7b89a5b445ba61a980bf5 100644 (file)
--- a/HOWTO
+++ b/HOWTO
@@ -886,7 +886,8 @@ Target file/device
        If this isn't set, fio will abort jobs that are destructive (e.g. that write)
        to what appears to be a mounted device or partition. This should help catch
        creating inadvertently destructive tests, not realizing that the test will
-       destroy data on the mounted file system. Default: false.
+       destroy data on the mounted file system. Note that some platforms don't allow
+       writing against a mounted device regardless of this option. Default: false.
 
 .. option:: pre_read=bool
 
@@ -1099,13 +1100,15 @@ I/O type
        blocks given. For example, if you give 32 as a parameter, fio will sync the
        file for every 32 writes issued. If fio is using non-buffered I/O, we may
        not sync the file. The exception is the sg I/O engine, which synchronizes
-       the disk cache anyway.
+       the disk cache anyway. Defaults to 0, which means no sync every certain
+       number of writes.
 
 .. option:: fdatasync=int
 
        Like :option:`fsync` but uses :manpage:`fdatasync(2)` to only sync data and
        not metadata blocks.  In Windows, FreeBSD, and DragonFlyBSD there is no
        :manpage:`fdatasync(2)`, this falls back to using :manpage:`fsync(2)`.
+       Defaults to 0, which means no sync data every certain number of writes.
 
 .. option:: write_barrier=int
 
@@ -1570,6 +1573,7 @@ I/O engine
                **sync**
                        Basic :manpage:`read(2)` or :manpage:`write(2)`
                        I/O. :manpage:`lseek(2)` is used to position the I/O location.
+                       See :option:`fsync` and :option:`fdatasync` for syncing write I/Os.
 
                **psync**
                        Basic :manpage:`pread(2)` or :manpage:`pwrite(2)` I/O.  Default on
@@ -1747,7 +1751,8 @@ caveat that when used on the command line, they must come after the
 
 .. option:: cpuload=int : [cpuio]
 
-       Attempt to use the specified percentage of CPU cycles.
+       Attempt to use the specified percentage of CPU cycles. This is a mandatory
+       option when using cpuio I/O engine.
 
 .. option:: cpuchunks=int : [cpuio]
 
@@ -2592,6 +2597,12 @@ Measurements and reporting
        all jobs in a file will be part of the same reporting group, unless
        separated by a :option:`stonewall`.
 
+.. option:: stats
+
+       By default, fio collects and shows final output results for all jobs
+       that run. If this option is set to 0, then fio will ignore it in
+       the final stat output.
+
 .. option:: write_bw_log=str
 
        If given, write a bandwidth log for this job. Can be used to store data of