diff --git a/tests/btrfs/121 b/tests/btrfs/121
new file mode 100755
index 000000000000..81b7deb047af
--- /dev/null
+++ b/tests/btrfs/121
@@ -0,0 +1,163 @@
+#! /bin/bash
+# FS QA Test 121
+#
+# This test verify the RAID1 reconstruction on the reappeared
+# device. By using the following steps:
+# Initialize a RAID1 with some data
+#
+# Re-mount RAID1 degraded with dev2 missing and write up to
+# half of the FS capacity.
+# Save md5sum checkpoint1
+#
+# Re-mount healthy RAID1
+#
+# Let balance re-silver.
+# Save md5sum checkpoint2
+#
+# Re-mount RAID1 degraded with dev1 missing
+# Save md5sum checkpoint3
+#
+# Verify if all three checkpoints match
+#
+#---------------------------------------------------------------------
+# Copyright (c) 2016 Oracle.  All Rights Reserved.
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License as
+# published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it would be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write the Free Software Foundation,
+# Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+#---------------------------------------------------------------------
+#
+
+seq=`basename $0`
+seqres=$RESULT_DIR/$seq
+echo "QA output created by $seq"
+
+here=`pwd`
+status=1	# failure is the default!
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+_cleanup()
+{
+	cd /
+}
+
+# get standard environment, filters and checks
+. ./common/rc
+. ./common/filter
+
+# remove previous $seqres.full before test
+rm -f $seqres.full
+
+# real QA test starts here
+
+_supported_fs btrfs
+_supported_os Linux
+_require_scratch_nocheck
+_require_scratch_dev_pool 2
+
+# the mounted test dir prevent btrfs unload, we need to unmount
+_test_unmount
+_require_btrfs_unloadable
+
+_scratch_dev_pool_get 2
+
+dev1=`echo $SCRATCH_DEV_POOL | awk '{print $1}'`
+dev2=`echo $SCRATCH_DEV_POOL | awk '{print $2}'`
+
+dev1_sz=`blockdev --getsize64 $dev1`
+dev2_sz=`blockdev --getsize64 $dev2`
+# get min of both
+max_fs_sz=`echo -e "$dev1_sz\n$dev2_sz" | sort | head -1`
+max_fs_sz=$(( max_fs_sz/2 ))
+if [ $max_fs_sz -gt 1000000 ]; then
+	bs="1M"
+	count=$(( max_fs_sz/1000000 ))
+else
+	max_fs_sz=$(( max_fs_sz*2 ))
+	_notrun "Smallest dev size $max_fs_sz, Need at least 2M"
+fi
+
+echo >> $seqres.full
+echo "max_fs_sz=$max_fs_sz count=$count" >> $seqres.full
+echo "-----Initialize -----" >> $seqres.full
+_scratch_pool_mkfs "-mraid1 -draid1" >> $seqres.full 2>&1
+_scratch_mount >> $seqres.full 2>&1
+_run_btrfs_util_prog filesystem show
+dd if=/dev/zero of="$SCRATCH_MNT"/tf1 bs=$bs count=1 \
+					>>$seqres.full 2>&1
+count=$(( count-- ))
+echo "unmount" >> $seqres.full
+echo "clean btrfs ko" >> $seqres.full
+_scratch_unmount
+_reload_btrfs_ko
+
+
+echo >> $seqres.full
+echo "-----Write degraded mount fill upto $max_fs_sz bytes-----" >> $seqres.full
+echo
+echo "Write data with degraded mount"
+# Since we didn't run dev scan, btrfs kernel does not know
+# about the dev2
+# don't use _scratch_mount as we want to control
+# the device used for mounting.
+
+_mount -o degraded $dev1 $SCRATCH_MNT >>$seqres.full 2>&1
+_run_btrfs_util_prog filesystem show
+dd if=/dev/zero of="$SCRATCH_MNT"/tf2 bs=$bs count=$count \
+					>>$seqres.full 2>&1
+checkpoint1=`md5sum $SCRATCH_MNT/tf2`
+echo $checkpoint1 >> $seqres.full 2>&1
+_scratch_unmount
+echo "unmount" >> $seqres.full
+
+echo >> $seqres.full
+echo "-----Mount normal-----" >> $seqres.full
+echo
+echo "Mount normal after balance"
+_run_btrfs_util_prog device scan
+_scratch_mount >> $seqres.full 2>&1
+_run_btrfs_util_prog filesystem show
+echo >> $seqres.full
+_run_btrfs_util_prog balance start ${SCRATCH_MNT}
+
+checkpoint2=`md5sum $SCRATCH_MNT/tf2`
+echo $checkpoint2 >> $seqres.full 2>&1
+
+echo >> $seqres.full
+echo "-----Mount degraded but with other dev -----" >> $seqres.full
+echo
+echo "Mount degraded but with other dev"
+_scratch_unmount
+_reload_btrfs_ko
+_mount -o degraded $dev2 $SCRATCH_MNT >>$seqres.full 2>&1
+_run_btrfs_util_prog filesystem show
+checkpoint3=`md5sum $SCRATCH_MNT/tf2`
+echo $checkpoint3 >> $seqres.full 2>&1
+
+if [ "$checkpoint1" != "$checkpoint2" ]; then
+	echo $checkpoint1
+	echo $checkpoint2
+	_fail "Inital sum does not match with after balance"
+fi
+
+if [ "$checkpoint1" != "$checkpoint3" ]; then
+	echo $checkpoint1
+	echo $checkpoint3
+	_fail "Inital sum does not match with data on dev2 written by balance"
+fi
+
+_scratch_dev_pool_put
+_test_mount
+
+echo "Silence is golden"
+status=0
+exit
diff --git a/tests/btrfs/121.out b/tests/btrfs/121.out
new file mode 100644
index 000000000000..0728787d17bc
--- /dev/null
+++ b/tests/btrfs/121.out
@@ -0,0 +1,8 @@
+QA output created by 121
+
+Write data with degraded mount
+
+Mount normal after balance
+
+Mount degraded but with other dev
+Silence is golden
diff --git a/tests/btrfs/group b/tests/btrfs/group
index 90af8fc2d106..5c28a3ca0687 100644
--- a/tests/btrfs/group
+++ b/tests/btrfs/group
@@ -122,3 +122,4 @@
 118 auto quick snapshot metadata
 119 auto quick snapshot metadata qgroup
 120 auto quick snapshot metadata
+121 auto replace
