diff --git a/test/shell/writecache-large.sh b/test/shell/writecache-large.sh
new file mode 100644
index 000000000..b52eaf6ab
--- /dev/null
+++ b/test/shell/writecache-large.sh
@@ -0,0 +1,153 @@
+#!/usr/bin/env bash
+
+# Copyright (C) 2018 Red Hat, Inc. All rights reserved.
+#
+# This copyrighted material is made available to anyone wishing to use,
+# modify, copy, or redistribute it subject to the terms and conditions
+# of the GNU General Public License v.2.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software Foundation,
+# Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+
+# Test writecache usage
+
+SKIP_WITH_LVMPOLLD=1
+
+. lib/inittest
+
+aux have_writecache 1 0 0 || skip
+which mkfs.xfs || skip
+
+# scsi_debug devices with 512 LBS 512 PBS
+aux prepare_scsi_debug_dev 1200
+check sysfs "$(< SCSI_DEBUG_DEV)" queue/logical_block_size "512"
+check sysfs "$(< SCSI_DEBUG_DEV)" queue/physical_block_size "512"
+
+aux prepare_devs 2 600
+blockdev --getss "$dev1"
+blockdev --getpbsz "$dev1"
+blockdev --getss "$dev2"
+blockdev --getpbsz "$dev2"
+
+mnt="mnt"
+mkdir -p $mnt
+
+for i in `seq 1 16384`; do echo -n "A" >> fileA; done
+for i in `seq 1 16384`; do echo -n "B" >> fileB; done
+for i in `seq 1 16384`; do echo -n "C" >> fileC; done
+
+# generate random data
+dd if=/dev/urandom of=randA bs=512K count=2
+dd if=/dev/urandom of=randB bs=512K count=3
+dd if=/dev/urandom of=randC bs=512K count=4
+
+_add_new_data_to_mnt() {
+	mkfs.xfs -f "$DM_DEV_DIR/$vg/$lv1"
+
+	mount "$DM_DEV_DIR/$vg/$lv1" $mnt
+
+	# add original data
+	cp randA $mnt
+	cp randB $mnt
+	cp randC $mnt
+	mkdir $mnt/1
+	cp fileA $mnt/1
+	cp fileB $mnt/1
+	cp fileC $mnt/1
+	mkdir $mnt/2
+	cp fileA $mnt/2
+	cp fileB $mnt/2
+	cp fileC $mnt/2
+	sync
+}
+
+_add_more_data_to_mnt() {
+	mkdir $mnt/more
+	cp fileA $mnt/more
+	cp fileB $mnt/more
+	cp fileC $mnt/more
+	cp randA $mnt/more
+	cp randB $mnt/more
+	cp randC $mnt/more
+	sync
+}
+
+_verify_data_on_mnt() {
+	diff randA $mnt/randA
+	diff randB $mnt/randB
+	diff randC $mnt/randC
+	diff fileA $mnt/1/fileA
+	diff fileB $mnt/1/fileB
+	diff fileC $mnt/1/fileC
+	diff fileA $mnt/2/fileA
+	diff fileB $mnt/2/fileB
+	diff fileC $mnt/2/fileC
+}
+
+_verify_more_data_on_mnt() {
+	diff randA $mnt/more/randA
+	diff randB $mnt/more/randB
+	diff randC $mnt/more/randC
+	diff fileA $mnt/more/fileA
+	diff fileB $mnt/more/fileB
+	diff fileC $mnt/more/fileC
+}
+
+_verify_data_on_lv() {
+	lvchange -ay $vg/$lv1
+	mount "$DM_DEV_DIR/$vg/$lv1" $mnt
+	_verify_data_on_mnt
+	rm $mnt/randA
+	rm $mnt/randB
+	rm $mnt/randC
+	rm -rf $mnt/1
+	rm -rf $mnt/2
+	umount $mnt
+	lvchange -an $vg/$lv1
+}
+
+vgcreate $SHARED $vg "$dev1"
+vgextend $vg "$dev2"
+
+# Use a large enough size so that the cleaner will not
+# finish immediately when detaching, and will require
+# a secondary check from command top level.
+
+lvcreate -n $lv1 -L 560M -an $vg "$dev1"
+lvcreate -n $lv2 -L 500M -an $vg "$dev2"
+
+lvchange -ay $vg/$lv1
+blockdev --getss "$DM_DEV_DIR/$vg/$lv1" 
+blockdev --getpbsz "$DM_DEV_DIR/$vg/$lv1" 
+
+lvconvert --yes --type writecache --cachevol $lv2 $vg/$lv1
+dmsetup table $vg-$lv1
+blockdev --getss "$DM_DEV_DIR/$vg/$lv1" 
+blockdev --getpbsz "$DM_DEV_DIR/$vg/$lv1" 
+
+_add_new_data_to_mnt
+_add_more_data_to_mnt
+_verify_data_on_mnt
+
+dd if=/dev/zero of=$mnt/big1 bs=1M count=100 oflag=sync
+dd if=/dev/zero of=$mnt/big2 bs=1M count=100 oflag=sync
+dd if=/dev/zero of=$mnt/big3 bs=1M count=100 oflag=sync
+dd if=/dev/zero of=$mnt/big4 bs=1M count=100 oflag=sync
+
+lvconvert --splitcache $vg/$lv1
+check lv_field $vg/$lv1 segtype linear
+check lv_field $vg/$lv2 segtype linear
+dmsetup table $vg-$lv1
+_verify_data_on_mnt
+_verify_more_data_on_mnt
+dd if=$mnt/big4 of=/dev/null bs=1M count=100
+umount $mnt
+lvchange -an $vg/$lv1
+_verify_data_on_lv
+lvchange -an $vg/$lv2
+lvremove $vg/$lv1
+lvremove $vg/$lv2
+
+vgremove -ff $vg
+
diff --git a/test/shell/writecache-split.sh b/test/shell/writecache-split.sh
index 9553ade0c..e615e2a13 100644
--- a/test/shell/writecache-split.sh
+++ b/test/shell/writecache-split.sh
@@ -84,7 +84,6 @@ lvconvert --splitcache $vg/$lv1
 lvs -o segtype $vg/$lv1 | grep linear
 lvs -o segtype $vg/$lv2 | grep linear
 
-lvchange -ay $vg/$lv1
 mount_umount $lv1
 lvchange -an $vg/$lv1
 
diff --git a/test/shell/writecache.sh b/test/shell/writecache.sh
index 8852e93f4..39ef31930 100644
--- a/test/shell/writecache.sh
+++ b/test/shell/writecache.sh
@@ -19,152 +19,251 @@ SKIP_WITH_LVMPOLLD=1
 aux have_writecache 1 0 0 || skip
 which mkfs.xfs || skip
 
-mount_dir="mnt"
-mkdir -p $mount_dir
-
-# generate random data
-dd if=/dev/urandom of=pattern1 bs=512K count=1
-
+# scsi_debug devices with 512 LBS 512 PBS
+aux prepare_scsi_debug_dev 256
+check sysfs "$(< SCSI_DEBUG_DEV)" queue/logical_block_size "512"
+check sysfs "$(< SCSI_DEBUG_DEV)" queue/physical_block_size "512"
 aux prepare_devs 2 64
 
-vgcreate $SHARED $vg "$dev1"
+# scsi_debug devices with 512 LBS and 4K PBS
+#aux prepare_scsi_debug_dev 256 sector_size=512 physblk_exp=3
+#check sysfs "$(< SCSI_DEBUG_DEV)" queue/logical_block_size "512"
+#check sysfs "$(< SCSI_DEBUG_DEV)" queue/physical_block_size "4096"
+#aux prepare_devs 2 64
 
+# loop devs with 512 LBS and 512 PBS
+#dd if=/dev/zero of=loopa bs=$((1024*1024)) count=64 2> /dev/null
+#dd if=/dev/zero of=loopb bs=$((1024*1024)) count=64 2> /dev/null
+#LOOP1=$(losetup -f loopa --show)
+#LOOP2=$(losetup -f loopb --show)
+#aux extend_filter "a|$LOOP1|"
+#aux extend_filter "a|$LOOP2|"
+#aux lvmconf 'devices/scan = "/dev"'
+#dev1=$LOOP1
+#dev2=$LOOP2
+
+# loop devs with 4096 LBS and 4096 PBS
+#dd if=/dev/zero of=loopa bs=$((1024*1024)) count=64 2> /dev/null
+#dd if=/dev/zero of=loopb bs=$((1024*1024)) count=64 2> /dev/null
+#LOOP1=$(losetup -f loopa --sector-size 4096 --show)
+#LOOP2=$(losetup -f loopb --sector-size 4096 --show)
+#aux extend_filter "a|$LOOP1|"
+#aux extend_filter "a|$LOOP2|"
+#aux lvmconf 'devices/scan = "/dev"'
+#dev1=$LOOP1
+#dev2=$LOOP2
+
+# the default is brd ram devs with 512 LBS 4K PBS
+# aux prepare_devs 2 64
+
+blockdev --getss "$dev1"
+blockdev --getpbsz "$dev1"
+blockdev --getss "$dev2"
+blockdev --getpbsz "$dev2"
+
+
+mnt="mnt"
+mkdir -p $mnt
+
+for i in `seq 1 16384`; do echo -n "A" >> fileA; done
+for i in `seq 1 16384`; do echo -n "B" >> fileB; done
+for i in `seq 1 16384`; do echo -n "C" >> fileC; done
+
+# generate random data
+dd if=/dev/urandom of=randA bs=512K count=2
+dd if=/dev/urandom of=randB bs=512K count=3
+dd if=/dev/urandom of=randC bs=512K count=4
+
+_add_new_data_to_mnt() {
+	mkfs.xfs -f "$DM_DEV_DIR/$vg/$lv1"
+
+	mount "$DM_DEV_DIR/$vg/$lv1" $mnt
+
+	# add original data
+	cp randA $mnt
+	cp randB $mnt
+	cp randC $mnt
+	mkdir $mnt/1
+	cp fileA $mnt/1
+	cp fileB $mnt/1
+	cp fileC $mnt/1
+	mkdir $mnt/2
+	cp fileA $mnt/2
+	cp fileB $mnt/2
+	cp fileC $mnt/2
+	sync
+}
+
+_add_more_data_to_mnt() {
+	mkdir $mnt/more
+	cp fileA $mnt/more
+	cp fileB $mnt/more
+	cp fileC $mnt/more
+	cp randA $mnt/more
+	cp randB $mnt/more
+	cp randC $mnt/more
+	sync
+}
+
+_verify_data_on_mnt() {
+	diff randA $mnt/randA
+	diff randB $mnt/randB
+	diff randC $mnt/randC
+	diff fileA $mnt/1/fileA
+	diff fileB $mnt/1/fileB
+	diff fileC $mnt/1/fileC
+	diff fileA $mnt/2/fileA
+	diff fileB $mnt/2/fileB
+	diff fileC $mnt/2/fileC
+}
+
+_verify_more_data_on_mnt() {
+	diff randA $mnt/more/randA
+	diff randB $mnt/more/randB
+	diff randC $mnt/more/randC
+	diff fileA $mnt/more/fileA
+	diff fileB $mnt/more/fileB
+	diff fileC $mnt/more/fileC
+}
+
+_verify_data_on_lv() {
+	lvchange -ay $vg/$lv1
+	mount "$DM_DEV_DIR/$vg/$lv1" $mnt
+	_verify_data_on_mnt
+	rm $mnt/randA
+	rm $mnt/randB
+	rm $mnt/randC
+	rm -rf $mnt/1
+	rm -rf $mnt/2
+	umount $mnt
+	lvchange -an $vg/$lv1
+}
+
+
+vgcreate $SHARED $vg "$dev1"
 vgextend $vg "$dev2"
 
+blockdev --getss "$dev1"
+blockdev --getpbsz "$dev1"
+blockdev --getss "$dev2"
+blockdev --getpbsz "$dev2"
+
+# Test attach while inactive, detach while inactive
+# create fs on LV before writecache is attached
+
 lvcreate -n $lv1 -l 8 -an $vg "$dev1"
-
 lvcreate -n $lv2 -l 4 -an $vg "$dev2"
-
-# test1: create fs on LV before writecache is attached
-
 lvchange -ay $vg/$lv1
-
-mkfs.xfs -f -s size=4096 "$DM_DEV_DIR/$vg/$lv1"
-
-mount "$DM_DEV_DIR/$vg/$lv1" $mount_dir
-
-cp pattern1 $mount_dir/pattern1
-
-umount $mount_dir
+_add_new_data_to_mnt
+umount $mnt
 lvchange -an $vg/$lv1
-
 lvconvert --yes --type writecache --cachevol $lv2 $vg/$lv1
-
 check lv_field $vg/$lv1 segtype writecache
-
 lvs -a $vg/${lv2}_cvol --noheadings -o segtype >out
 grep linear out
-
 lvchange -ay $vg/$lv1
-
-mount "$DM_DEV_DIR/$vg/$lv1" $mount_dir
-
-diff pattern1 $mount_dir/pattern1
-
-cp pattern1 $mount_dir/pattern1b
-
-ls -l $mount_dir
-
-umount $mount_dir
-
+blockdev --getss "$DM_DEV_DIR/$vg/$lv1"
+blockdev --getpbsz "$DM_DEV_DIR/$vg/$lv1"
+mount "$DM_DEV_DIR/$vg/$lv1" $mnt
+_add_more_data_to_mnt
+_verify_data_on_mnt
+_verify_more_data_on_mnt
+umount $mnt
 lvchange -an $vg/$lv1
-
 lvconvert --splitcache $vg/$lv1
-
 check lv_field $vg/$lv1 segtype linear
 check lv_field $vg/$lv2 segtype linear
-
 lvchange -ay $vg/$lv1
-lvchange -ay $vg/$lv2
-
-mount "$DM_DEV_DIR/$vg/$lv1" $mount_dir
-
-ls -l $mount_dir
-
-diff pattern1 $mount_dir/pattern1
-diff pattern1 $mount_dir/pattern1b
-
-umount $mount_dir
+blockdev --getss "$DM_DEV_DIR/$vg/$lv1"
+blockdev --getpbsz "$DM_DEV_DIR/$vg/$lv1"
 lvchange -an $vg/$lv1
+_verify_data_on_lv
 lvchange -an $vg/$lv2
-
-# test2: create fs on LV after writecache is attached
-
-lvconvert --yes --type writecache --cachevol $lv2 $vg/$lv1
-
-check lv_field $vg/$lv1 segtype writecache
-
-lvs -a $vg/${lv2}_cvol --noheadings -o segtype >out
-grep linear out
-
-lvchange -ay $vg/$lv1
-
-mkfs.xfs -f -s size=4096 "$DM_DEV_DIR/$vg/$lv1"
-
-mount "$DM_DEV_DIR/$vg/$lv1" $mount_dir
-
-cp pattern1 $mount_dir/pattern1
-ls -l $mount_dir
-
-umount $mount_dir
-lvchange -an $vg/$lv1
-
-lvconvert --splitcache $vg/$lv1
-
-check lv_field $vg/$lv1 segtype linear
-check lv_field $vg/$lv2 segtype linear
-
-lvchange -ay $vg/$lv1
-lvchange -ay $vg/$lv2
-
-mount "$DM_DEV_DIR/$vg/$lv1" $mount_dir
-
-ls -l $mount_dir
-
-diff pattern1 $mount_dir/pattern1
-
-umount $mount_dir
-lvchange -an $vg/$lv1
-lvchange -an $vg/$lv2
-
-
-# test3: attach writecache to an active LV
-
-lvchange -ay $vg/$lv1
-
-mkfs.xfs -f -s size=4096 "$DM_DEV_DIR/$vg/$lv1"
-
-mount "$DM_DEV_DIR/$vg/$lv1" $mount_dir
-
-cp pattern1 $mount_dir/pattern1
-ls -l $mount_dir
-
-# TODO BZ 1808012 - can not convert active volume to writecache:
-not lvconvert --yes --type writecache --cachevol $lv2 $vg/$lv1
-
-if false; then
-check lv_field $vg/$lv1 segtype writecache
-
-lvs -a $vg/${lv2}_cvol --noheadings -o segtype >out
-grep linear out
-
-cp pattern1 $mount_dir/pattern1.after
-
-diff pattern1 $mount_dir/pattern1
-diff pattern1 $mount_dir/pattern1.after
-
-umount $mount_dir
-lvchange -an $vg/$lv1
-lvchange -ay $vg/$lv1
-mount "$DM_DEV_DIR/$vg/$lv1" $mount_dir
-
-diff pattern1 $mount_dir/pattern1
-diff pattern1 $mount_dir/pattern1.after
-fi
-
-umount $mount_dir
-lvchange -an $vg/$lv1
 lvremove $vg/$lv1
+lvremove $vg/$lv2
 
+# Test attach while inactive, detach while inactive
+# create fs on LV after writecache is attached
+
+lvcreate -n $lv1 -l 8 -an $vg "$dev1"
+lvcreate -n $lv2 -l 4 -an $vg "$dev2"
+lvconvert --yes --type writecache --cachevol $lv2 $vg/$lv1
+check lv_field $vg/$lv1 segtype writecache
+lvs -a $vg/${lv2}_cvol --noheadings -o segtype >out
+grep linear out
+lvchange -ay $vg/$lv1
+blockdev --getss "$DM_DEV_DIR/$vg/$lv1"
+blockdev --getpbsz "$DM_DEV_DIR/$vg/$lv1"
+_add_new_data_to_mnt
+umount $mnt
+lvchange -an $vg/$lv1
+lvconvert --splitcache $vg/$lv1
+lvchange -ay $vg/$lv1
+blockdev --getss "$DM_DEV_DIR/$vg/$lv1"
+blockdev --getpbsz "$DM_DEV_DIR/$vg/$lv1"
+mount "$DM_DEV_DIR/$vg/$lv1" $mnt
+_add_more_data_to_mnt
+_verify_data_on_mnt
+_verify_more_data_on_mnt
+umount $mnt
+lvchange -an $vg/$lv1
+_verify_data_on_lv
+lvremove $vg/$lv1
+lvremove $vg/$lv2
+
+# Test attach while active, detach while active
+
+lvcreate -n $lv1 -l 8 -an $vg "$dev1"
+lvcreate -n $lv2 -l 4 -an $vg "$dev2"
+lvchange -ay $vg/$lv1
+_add_new_data_to_mnt
+lvconvert --yes --type writecache --cachevol $lv2 $vg/$lv1
+blockdev --getss "$DM_DEV_DIR/$vg/$lv1"
+blockdev --getpbsz "$DM_DEV_DIR/$vg/$lv1"
+_add_more_data_to_mnt
+_verify_data_on_mnt
+lvconvert --splitcache $vg/$lv1
+check lv_field $vg/$lv1 segtype linear
+check lv_field $vg/$lv2 segtype linear
+blockdev --getss "$DM_DEV_DIR/$vg/$lv1"
+blockdev --getpbsz "$DM_DEV_DIR/$vg/$lv1"
+_verify_data_on_mnt
+_verify_more_data_on_mnt
+umount $mnt
+lvchange -an $vg/$lv1
+lvchange -an $vg/$lv2
+_verify_data_on_lv
+lvremove $vg/$lv1
+lvremove $vg/$lv2
+
+# FIXME: test depends on unpushed commit
+# that enables two stage flush using cleaner
+#
+# Test attach while active, detach while active,
+# skip cleaner so flush message is used instead
+# 
+# lvcreate -n $lv1 -l 8 -an $vg "$dev1"
+# lvcreate -n $lv2 -l 4 -an $vg "$dev2"
+# lvchange -ay $vg/$lv1
+# _add_new_data_to_mnt
+# lvconvert --yes --type writecache --cachevol $lv2 $vg/$lv1
+# blockdev --getss "$DM_DEV_DIR/$vg/$lv1"
+# blockdev --getpbsz "$DM_DEV_DIR/$vg/$lv1"
+# _add_more_data_to_mnt
+# _verify_data_on_mnt
+# lvconvert --splitcache --cachesettings cleaner=0 $vg/$lv1
+# check lv_field $vg/$lv1 segtype linear
+# check lv_field $vg/$lv2 segtype linear
+# blockdev --getss "$DM_DEV_DIR/$vg/$lv1"
+# blockdev --getpbsz "$DM_DEV_DIR/$vg/$lv1"
+# _verify_data_on_mnt
+# _verify_more_data_on_mnt
+# umount $mnt
+# lvchange -an $vg/$lv1
+# lvchange -an $vg/$lv2
+# _verify_data_on_lv
+# lvremove $vg/$lv1
+# lvremove $vg/$lv2
+ 
 vgremove -ff $vg
-
+