Expand on fill_device option since it apparently causes confusion

[fio.git] / HOWTO

diff --git a/HOWTO b/HOWTO
index 68e17e9f4743b6738fe10c1e329be9783f8af746..e8fbd97f6ab2693920b93101e654873005516f3a 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
 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
 
 blocksize=int
 bs=int         The block size used for the io units. Defaults to 4k. Values