Expand on fill_device option since it apparently causes confusion

Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

diff --git a/HOWTO b/HOWTO
index 68e17e9..e8fbd97 100644 (file)
--- a/HOWTO
+++ b/HOWTO
@@ -378,7 +378,11 @@ filesize=int       Individual file sizes. May be a range, in which case fio
 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. For a read workload, the mount
-               point will be filled first then IO started on the result.
+               point will be filled first then IO started on the result. This
+               option doesn't make sense if operating on a raw device node,
+               since the size of that is already known by the file system.
+               Additionally, writing beyond end-of-device will not return
+               ENOSPC there.
 
 blocksize=int
 bs=int         The block size used for the io units. Defaults to 4k. Values

diff --git a/fio.1 b/fio.1
index d372727..a6547ee 100644 (file)
--- a/fio.1
+++ b/fio.1
@@ -235,7 +235,9 @@ must be given.
 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.
 For a read workload, the mount point will be filled first then IO started on
-the result.
+the result. This option doesn't make sense if operating on a raw device node,
+since the size of that is already known by the file system. Additionally,
+writing beyond end-of-device will not return ENOSPC there.
 .TP
 .BI filesize \fR=\fPirange
 Individual file sizes. May be a range, in which case \fBfio\fR will select sizes