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

I think people could think sync ioengine and variants would somehow
fsync(2) for writes from what their name sound like, while they do
not unless these options are explicitly set (default 0).

Signed-off-by: Tomohiro Kusumi <tkusumi@tuxera.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

diff --git a/HOWTO b/HOWTO
index 1ce1b0c1b441f955b6ccfd03e6a2e802fcce5a28..cae95b7720f210893bb7b89a5b445ba61a980bf5 100644 (file)
--- a/HOWTO
+++ b/HOWTO
@@ -1100,13 +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
        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)`.
 
 .. 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
 
 
 .. option:: write_barrier=int
 


@@ -1571,6 +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.
                **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
 
                **psync**
                        Basic :manpage:`pread(2)` or :manpage:`pwrite(2)` I/O.  Default on