X-Git-Url: https://git.kernel.dk/?a=blobdiff_plain;ds=sidebyside;f=HOWTO;h=70eed2805c2d96811d4238afaed645f4f3a10e45;hb=47e6a6e5b5866412c3174eb09e488cd26a9d3b5f;hp=e1399b4a101925d94527542e4c5f8f696668912b;hpb=5de1d4ba1e6ae82bb4ad559463801cb6b7096ac3;p=fio.git

diff --git a/HOWTO b/HOWTO
index e1399b4a..70eed280 100644
--- a/HOWTO
+++ b/HOWTO
@@ -1329,7 +1329,9 @@ I/O type
 	and that some blocks may be read/written more than once. If this option is
 	used with :option:`verify` and multiple blocksizes (via :option:`bsrange`),
 	only intact blocks are verified, i.e., partially-overwritten blocks are
-	ignored.
+	ignored.  With an async I/O engine and an I/O depth > 1, it is possible for
+	the same block to be overwritten, which can cause verification errors.  Either
+	do not use norandommap in this case, or also use the lfsr random generator.
 
 .. option:: softrandommap=bool
 
@@ -2663,6 +2665,11 @@ Verification
 	previously written file. If the data direction includes any form of write,
 	the verify will be of the newly written data.
 
+	To avoid false verification errors, do not use the norandommap option when
+	verifying data with async I/O engines and I/O depths > 1.  Or use the
+	norandommap and the lfsr random generator together to avoid writing to the
+	same offset with muliple outstanding I/Os.
+
 .. option:: verify_offset=int
 
 	Swap the verification header with data somewhere else in the block before