diff --git a/tests/btrfs/266 b/tests/btrfs/266
index 42aff7c0..894c5c6e 100755
--- a/tests/btrfs/266
+++ b/tests/btrfs/266
@@ -25,7 +25,7 @@ _require_odirect
 _require_non_zoned_device "${SCRATCH_DEV}"
 
 _scratch_dev_pool_get 3
-# step 1, create a raid1 btrfs which contains one 128k file.
+# step 1, create a raid1 btrfs which contains one 192k file.
 echo "step 1......mkfs.btrfs"
 
 mkfs_opts="-d raid1c3 -b 1G"
@@ -33,7 +33,7 @@ _scratch_pool_mkfs $mkfs_opts >>$seqres.full 2>&1
 
 _scratch_mount
 
-$XFS_IO_PROG -f -d -c "pwrite -S 0xaa -b 256K 0 256K" \
+$XFS_IO_PROG -f -d -c "pwrite -S 0xaa -b 192K 0 192K" \
 	"$SCRATCH_MNT/foobar" | \
 	_filter_xfs_io_offset
 
@@ -56,6 +56,13 @@ devpath3=$(_btrfs_get_device_path ${logical} 3)
 
 _scratch_unmount
 
+# We corrupt the mirrors so that every 64K block only has one
+# good mirror. (X = corruption)
+#
+#		0	64K	128K	192K
+# Mirror 1	|XXXXXXXXXXXXXXX|	|
+# Mirror 2	|	|XXXXXXXXXXXXXXX|
+# Mirror 3	|XXXXXXX|	|XXXXXXX|
 $XFS_IO_PROG -d -c "pwrite -S 0xbd -b 64K $physical3 64K" \
 	$devpath3 > /dev/null
 
@@ -65,7 +72,7 @@ $XFS_IO_PROG -d -c "pwrite -S 0xba -b 64K $physical1 128K" \
 $XFS_IO_PROG -d -c "pwrite -S 0xbb -b 64K $((physical2 + 65536)) 128K" \
 	$devpath2 > /dev/null
 
-$XFS_IO_PROG -d -c "pwrite -S 0xbc -b 64K $((physical3 + (2 * 65536))) 128K"  \
+$XFS_IO_PROG -d -c "pwrite -S 0xbc -b 64K $((physical3 + (2 * 65536))) 64K"  \
 	$devpath3 > /dev/null
 
 _scratch_mount
@@ -73,19 +80,53 @@ _scratch_mount
 # step 3, 128k dio read (this read can repair bad copy)
 echo "step 3......repair the bad copy"
 
-_btrfs_buffered_read_on_mirror 0 3 "$SCRATCH_MNT/foobar" 0 256K
-_btrfs_buffered_read_on_mirror 1 3 "$SCRATCH_MNT/foobar" 0 256K
-_btrfs_buffered_read_on_mirror 2 3 "$SCRATCH_MNT/foobar" 0 256K
+_btrfs_buffered_read_on_mirror 0 3 "$SCRATCH_MNT/foobar" 0 192K
+_btrfs_buffered_read_on_mirror 1 3 "$SCRATCH_MNT/foobar" 0 192K
+_btrfs_buffered_read_on_mirror 2 3 "$SCRATCH_MNT/foobar" 0 192K
 
 _scratch_unmount
 
 echo "step 4......check if the repair worked"
-$XFS_IO_PROG -d -c "pread -v -b 512 $physical1 512" $devpath1 |\
+echo "Dev 1:"
+echo "  Physical offset + 0:"
+$XFS_IO_PROG -c "pread -qv $physical1 16" $devpath1 |\
 	_filter_xfs_io_offset
-$XFS_IO_PROG -d -c "pread -v -b 512 $physical2 512" $devpath2 |\
+echo "  Physical offset + 64K:"
+$XFS_IO_PROG -c "pread -qv $((physical1 + 65536)) 16" $devpath1 |\
 	_filter_xfs_io_offset
-$XFS_IO_PROG -d -c "pread -v -b 512 $physical3 512" $devpath3 |\
+echo "  Physical offset + 128K:"
+$XFS_IO_PROG -c "pread -qv $((physical1 + 131072)) 16" $devpath1 |\
 	_filter_xfs_io_offset
+echo
+
+echo "Dev 2:"
+echo "  Physical offset + 0:"
+$XFS_IO_PROG -c "pread -qv $physical2 16" $devpath2 |\
+	_filter_xfs_io_offset
+echo "  Physical offset + 64K:"
+$XFS_IO_PROG -c "pread -qv $((physical2 + 65536)) 16" $devpath2 |\
+	_filter_xfs_io_offset
+echo "  Physical offset + 128K:"
+$XFS_IO_PROG -c "pread -qv $((physical2 + 131072)) 16" $devpath2 |\
+	_filter_xfs_io_offset
+echo
+
+echo "Dev 3:"
+echo "  Physical offset + 0:"
+$XFS_IO_PROG -c "pread -v $physical3 16" $devpath3 |\
+	_filter_xfs_io_offset
+echo "  Physical offset + 64K:"
+$XFS_IO_PROG -c "pread -v $((physical3 + 65536)) 16" $devpath3 |\
+	_filter_xfs_io_offset
+echo "  Physical offset + 128K:"
+$XFS_IO_PROG -c "pread -v $((physical3 + 131072)) 16" $devpath3 |\
+	_filter_xfs_io_offset
+
+# Final step to use btrfs check to verify the csum of all mirrors.
+$BTRFS_UTIL_PROG check --check-data-csum $SCRATCH_DEV >> $seqres.full 2>&1
+if [ $? -ne 0 ]; then
+	echo "btrfs check found some data csum mismatch"
+fi
 
 _scratch_dev_pool_put
 # success, all done
diff --git a/tests/btrfs/266.out b/tests/btrfs/266.out
index fcf2f5b8..305e9c83 100644
--- a/tests/btrfs/266.out
+++ b/tests/btrfs/266.out
@@ -1,109 +1,36 @@
 QA output created by 266
 step 1......mkfs.btrfs
-wrote 262144/262144 bytes
+wrote 196608/196608 bytes
 XXX Bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 step 2......corrupt file extent
 step 3......repair the bad copy
 step 4......check if the repair worked
+Dev 1:
+  Physical offset + 0:
 XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
+  Physical offset + 64K:
 XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
+  Physical offset + 128K:
 XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
+
+Dev 2:
+  Physical offset + 0:
 XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
+  Physical offset + 64K:
 XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
+  Physical offset + 128K:
 XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
+
+Dev 3:
+  Physical offset + 0:
 XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-read 512/512 bytes
+read 16/16 bytes
 XXX Bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+  Physical offset + 64K:
 XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-read 512/512 bytes
+read 16/16 bytes
 XXX Bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+  Physical offset + 128K:
 XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-XXXXXXXX:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
-read 512/512 bytes
+read 16/16 bytes
 XXX Bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
