Update sample atomic write job file

Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/examples/fusion-aw-sync.fio b/examples/fusion-aw-sync.fio
index c4639f0..f2ca313 100644
--- a/examples/fusion-aw-sync.fio
+++ b/examples/fusion-aw-sync.fio
@@ -6,7 +6,10 @@
 blocksize=8k
 blockalign=8k
 
+# if file system supports atomic write
 filename=/mnt/fs/file
+# or test on a direct block device instead
+#filename=/dev/fioa
 randrepeat=1
 fallocate=none
 direct=1