[PATCH] Allow verification to be done at finer granularity

Allow verification to be done at a finer granularity than blocksize.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/HOWTO b/HOWTO
index b862d74..2797a58 100644
--- a/HOWTO
+++ b/HOWTO
@@ -602,6 +602,11 @@
 		can ignore this option unless doing huge amounts of really
 		fast IO where the red-black tree sorting CPU time becomes
 		significant.
+
+header_interval=siint	Write the verification header at a finer granularity
+			than the blocksize. It will be written for chunks the
+			size of header_interval. blocksize should divide this
+			evenly.
 		
 stonewall	Wait for preceeding jobs in the job file to exit, before
 		starting this one. Can be used to insert serialization