diff --git a/misc/mdcheck b/misc/mdcheck
index 398a1ea6..fcd38e2a 100644
--- a/misc/mdcheck
+++ b/misc/mdcheck
@@ -21,42 +21,96 @@
 #
 # It supports a 'time budget' such that any incomplete 'check'
 # will be checkpointed when that time has expired.
-# A subsequent invocation can allow the 'check' to continue.
+# A subsequent invocation will allow the 'check' to continue.
+#
+# Arrays are identified by UUID and the 'sync_completed' value is stored
+# in /var/lib/mdcheck/MD_UUID_$UUID. When the script has finished checking
+# an array, it creates a file /var/lib/mdcheck/Checked_$UUID.
+#
+# Modes are:
+#   --continue      Don't start new checks, only continue previously started ones
+#                   for which MD_UUID_$UUID already exists
+#   --maybe-start   Like --continue, but also start new checks for arrays for which
+#                   Checked_$UUID does not exist.
+#   --restart:      Enable restarting checks that were previously finished
+#                   (remove all Checked_* files) and exit immediately.
+#                   This mode doesn't start any array checks.
+#   --force-start:  A new check from 0 will be started on all arrays, even those
+#                   that hadn't finished before.
+#
+# With none of these options given, the mode defaults to --force-start
+# for backward compatibility reasons.
 #
 # Options are:
-#   --continue    Don't start new checks, only continue old ones.
 #   --duration    This is passed to "date --date=$duration" to find out
 #		  when to finish
-#
-# To support '--continue', arrays are identified by UUID and the 'sync_completed'
-# value is stored  in /var/lib/mdcheck/$UUID
-
-# convert a /dev/md name into /sys/.../md equivalent
-sysname() {
-	set `ls -lLd $1`
-	maj=${5%,}
-	min=$6
-	readlink -f /sys/dev/block/$maj:$min
+
+
+# If the script is run from systemd, simply write to the journal on stderr.
+# Otherwise, use logger.
+log() {
+    if [[ "$INVOCATION_ID" ]]; then
+	    echo "$@" >&2
+    else
+	    logger -p daemon.info "mdcheck: $*"
+    fi
+}
+
+# get device name from sysfs
+devname() {
+    local dev
+    [[ -f "$1/uevent" ]] && \
+	    dev=$(. "$1/uevent" && echo -n "$DEVNAME")
+    [[ "$dev" && -b "/dev/$dev" ]] || return 1
+    echo -n "/dev/$dev"
+}
+
+usage() {
+    echo >&2 'Usage: mdcheck [mode] [options]
+
+Mode:
+	--help		print this help
+	--continue	only continue previously started checks
+	--maybe-start	continue, and start check on arrays that have not been checked
+	--restart	re-enable checking previously finished arrays
+	--force-start	start checking all arrays from zero (default)
+Options:
+	--duration	time-offset (must be understood by "date --date")'
 }
 
-args=$(getopt -o hcd: -l help,continue,duration: -n mdcheck -- "$@")
+set_mode() {
+    [[ "$MODE" ]] && {
+        echo >&2 'ERROR: only one of --continue, --maybe-start, --restart, or --force-start may be set
+'
+	usage
+	exit 1
+    }
+    MODE=$1
+}
+
+args=$(getopt -o hcmrfd: -l help,continue,maybe-start,restart,force-start,duration: -n mdcheck -- "$@")
 rv=$?
-if [ $rv -ne 0 ]; then exit $rv; fi
+if [ $rv -ne 0 ]; then
+	usage
+	exit $rv
+fi
 
 eval set -- $args
 
-cont=
+MODE=
 endtime=
 while [ " $1" != " --" ]
 do
     case $1 in
 	--help )
-		echo >&2 'Usage: mdcheck [--continue] [--duration time-offset]'
-		echo >&2 '  time-offset must be understood by "date --date"'
+		usage
 		exit 0
 		;;
-	--continue ) cont=yes ;;
-	--duration ) shift; dur=$1
+	--continue|--maybe-start|--restart|--force-start)
+		set_mode "$1"
+		;;
+	--duration )
+		shift; dur=$1
 		endtime=$(date --date "$dur" "+%s")
 		;;
     esac
@@ -64,6 +118,31 @@ do
 done
 shift
 
+[[ $# -eq 0 ]] || {
+    usage
+    exit 1
+}
+
+[[ "$MODE" ]] || {
+    echo >&2 'mdcheck: WARNING: no mode specified, defaulting to --force-start'
+    echo >&2 '=== Type ctrl-c within 5 seconds if this is not intended'
+    sleep 5
+    set_mode --force-start
+    echo >&2 'mdcheck is running in --force-start mode.'
+}
+
+case $MODE in
+    --restart)
+	    log 'Re-enabling array checks for previously finished arrays'
+	    rm -f /var/lib/mdcheck/Checked_*
+	    exit 0
+	    ;;
+    --force-start)
+	    log 'Forcing array check from 0 for all arrays'
+	    rm -f /var/lib/mdcheck/Checked_* /var/lib/mdcheck/MD_UUID_*
+	    ;;
+esac
+
 # We need a temp file occasionally...
 tmp=/var/lib/mdcheck/.md-check-$$
 cnt=0
@@ -87,7 +166,7 @@ cleanup() {
 	fi
 	echo idle > $sys/md/sync_action
 	cat $sys/md/sync_min > $fl
-	logger -p daemon.info pause checking $dev at `cat $fl`
+	log pause checking $dev at `cat $fl`
     done
     rm -f "$tmp"
 }
@@ -100,42 +179,41 @@ mkdir -p /var/lib/mdcheck
 find /var/lib/mdcheck -name "MD_UUID*" -type f -mtime +180 -exec rm {} \;
 
 # Now look at each md device.
-for dev in /dev/md?*
+for sync_act in /sys/block/*/md/sync_action
 do
-	[ -e "$dev" ] || continue
-	sys=`sysname $dev`
-	if [ ! -f "$sys/md/sync_action" ]
-	then # cannot check this array
-		continue
-	fi
-	if [ "`cat $sys/md/sync_action`" != 'idle' ]
+	[ -e "$sync_act" ] || continue
+	if [ "`cat $sync_act`" != 'idle' ]
 	then # This array is busy
 		continue
 	fi
 
+	sys=${sync_act%/md/*}
+	dev=$(devname "$sys") || continue
 	mdadm --detail --export "$dev" | grep '^MD_UUID=' > $tmp || continue
 	source $tmp
+	[[ "$MD_UUID" ]] || continue
+
 	fl="/var/lib/mdcheck/MD_UUID_$MD_UUID"
-	if [ -z "$cont" ]
-	then
+	checked="${fl/MD_UUID_/Checked_}"
+	if [[ -f "$fl" ]]; then
+		[[ ! -f "$checked" ]] || {
+		    log "WARNING: $checked exists, continuing anyway"
+		}
+		start=`cat "$fl"`
+	elif [[ ! -f "$checked" && "$MODE" != --continue ]]; then
 		start=0
-		logger -p daemon.info mdcheck start checking $dev
-	elif [ -z "$MD_UUID" -o ! -f "$fl" ]
-	then
-		# Nothing to continue here
+	else # nothing to do
 		continue
-	else
-		start=`cat "$fl"`
-		logger -p daemon.info mdcheck continue checking $dev from $start
 	fi
 
-	cnt=$[cnt+1]
+	: "$((cnt+=1))"
 	eval MD_${cnt}_fl=\$fl
 	eval MD_${cnt}_sys=\$sys
 	eval MD_${cnt}_dev=\$dev
 	echo $start > $fl
 	echo $start > $sys/md/sync_min
 	echo check > $sys/md/sync_action
+	log checking $dev from $start
 done
 
 if [ -z "$endtime" ]
@@ -156,9 +234,10 @@ do
 
 		if [ "`cat $sys/md/sync_action`" != 'check' ]
 		then
-			logger -p daemon.info mdcheck finished checking $dev
+			log finished checking $dev
 			eval MD_${i}_fl=
-			rm -f $fl
+			rm -f "$fl"
+			touch "${fl/MD_UUID_/Checked_}"
 			continue;
 		fi
 		read a rest < $sys/md/sync_completed
diff --git a/systemd/mdcheck_continue.service b/systemd/mdcheck_continue.service
index cd12db85..035fd61f 100644
--- a/systemd/mdcheck_continue.service
+++ b/systemd/mdcheck_continue.service
@@ -7,10 +7,11 @@
 
 [Unit]
 Description=MD array scrubbing - continuation
-ConditionPathExistsGlob=/var/lib/mdcheck/MD_UUID_*
 Documentation=man:mdadm(8)
 
 [Service]
 Type=simple
 Environment="MDADM_CHECK_DURATION=6 hours"
-ExecStart=/usr/share/mdadm/mdcheck --continue --duration ${MDADM_CHECK_DURATION}
+# mdcheck --maybe-start will continues previously started checks, and starts from
+# zero for arrays without a "Checked_$UUID" marker in /var/lib/mdcheck
+ExecStart=/usr/share/mdadm/mdcheck --maybe-start --duration ${MDADM_CHECK_DURATION}
diff --git a/systemd/mdcheck_start.service b/systemd/mdcheck_start.service
index 16ba6b67..c7ddd4f6 100644
--- a/systemd/mdcheck_start.service
+++ b/systemd/mdcheck_start.service
@@ -12,5 +12,4 @@ Documentation=man:mdadm(8)
 
 [Service]
 Type=simple
-Environment="MDADM_CHECK_DURATION=6 hours"
-ExecStart=/usr/share/mdadm/mdcheck --duration ${MDADM_CHECK_DURATION}
+ExecStart=/usr/share/mdadm/mdcheck --restart
diff --git a/systemd/mdcheck_start.timer b/systemd/mdcheck_start.timer
index 1b8f3f20..8d09b3f6 100644
--- a/systemd/mdcheck_start.timer
+++ b/systemd/mdcheck_start.timer
@@ -9,7 +9,7 @@
 Description=MD array scrubbing
 
 [Timer]
-OnCalendar=Sun *-*-1..7 1:05:00
+OnCalendar=Sun *-*-1..7 0:45:00
 
 [Install]
 WantedBy= mdmonitor.service