diff --git a/compact.go b/compact.go
index 310c162f6..d3ca6edfa 100644
--- a/compact.go
+++ b/compact.go
@@ -70,7 +70,7 @@ func newCompactorMetrics(r prometheus.Registerer) *compactorMetrics {
 		Name: "tsdb_compactions_failed_total",
 		Help: "Total number of compactions that failed for the partition.",
 	})
-	m.duration = prometheus.NewHistogram(prometheus.HistogramOpts{
+	m.duration = prometheus.NewSummary(prometheus.SummaryOpts{
 		Name: "tsdb_compaction_duration",
 		Help: "Duration of compaction runs.",
 	})
@@ -219,6 +219,7 @@ func (c *compactor) write(uid ulid.ULID, blocks ...Block) (err error) {
 		if err != nil {
 			c.metrics.failed.Inc()
 		}
+		c.metrics.ran.Inc()
 		c.metrics.duration.Observe(time.Since(t).Seconds())
 	}(time.Now())
 
diff --git a/db.go b/db.go
index a376f465e..74b834b0c 100644
--- a/db.go
+++ b/db.go
@@ -122,13 +122,42 @@ type DB struct {
 }
 
 type dbMetrics struct {
+	activeAppenders      prometheus.Gauge
+	loadedBlocks         prometheus.GaugeFunc
+	reloads              prometheus.Counter
+	reloadsFailed        prometheus.Counter
+	reloadDuration       prometheus.Summary
 	samplesAppended      prometheus.Counter
 	compactionsTriggered prometheus.Counter
 }
 
-func newDBMetrics(r prometheus.Registerer) *dbMetrics {
+func newDBMetrics(db *DB, r prometheus.Registerer) *dbMetrics {
 	m := &dbMetrics{}
 
+	m.activeAppenders = prometheus.NewGauge(prometheus.GaugeOpts{
+		Name: "tsdb_active_appenders",
+		Help: "Number of currently active appender transactions",
+	})
+	m.loadedBlocks = prometheus.NewGaugeFunc(prometheus.GaugeOpts{
+		Name: "tsdb_blocks_loaded",
+		Help: "Number of currently loaded data blocks",
+	}, func() float64 {
+		db.mtx.RLock()
+		defer db.mtx.RUnlock()
+		return float64(len(db.blocks))
+	})
+	m.reloads = prometheus.NewCounter(prometheus.CounterOpts{
+		Name: "tsdb_reloads_total",
+		Help: "Number of times the database reloaded block data from disk.",
+	})
+	m.reloadsFailed = prometheus.NewCounter(prometheus.CounterOpts{
+		Name: "tsdb_reloads_failures_total",
+		Help: "Number of times the database failed to reload black data from disk.",
+	})
+	m.reloadDuration = prometheus.NewSummary(prometheus.SummaryOpts{
+		Name: "tsdb_reload_duration_seconds",
+		Help: "Duration of block reloads.",
+	})
 	m.samplesAppended = prometheus.NewCounter(prometheus.CounterOpts{
 		Name: "tsdb_samples_appended_total",
 		Help: "Total number of appended sampledb.",
@@ -140,6 +169,11 @@ func newDBMetrics(r prometheus.Registerer) *dbMetrics {
 
 	if r != nil {
 		r.MustRegister(
+			m.activeAppenders,
+			m.loadedBlocks,
+			m.reloads,
+			m.reloadsFailed,
+			m.reloadDuration,
 			m.samplesAppended,
 			m.compactionsTriggered,
 		)
@@ -165,12 +199,13 @@ func Open(dir string, l log.Logger, r prometheus.Registerer, opts *Options) (db
 	db = &DB{
 		dir:      dir,
 		logger:   l,
-		metrics:  newDBMetrics(r),
 		opts:     opts,
 		compactc: make(chan struct{}, 1),
 		donec:    make(chan struct{}),
 		stopc:    make(chan struct{}),
 	}
+	db.metrics = newDBMetrics(db, r)
+
 	if !opts.NoLockfile {
 		absdir, err := filepath.Abs(dir)
 		if err != nil {
@@ -374,7 +409,15 @@ func (db *DB) getBlock(id ulid.ULID) (Block, bool) {
 	return nil, false
 }
 
-func (db *DB) reloadBlocks() error {
+func (db *DB) reloadBlocks() (err error) {
+	defer func(t time.Time) {
+		if err != nil {
+			db.metrics.reloadsFailed.Inc()
+		}
+		db.metrics.reloads.Inc()
+		db.metrics.reloadDuration.Observe(time.Since(t).Seconds())
+	}(time.Now())
+
 	var cs []io.Closer
 	defer func() { closeAll(cs...) }()
 
@@ -447,7 +490,7 @@ func validateBlockSequence(bs []Block) error {
 	prev := bs[0]
 	for _, b := range bs[1:] {
 		if b.Meta().MinTime < prev.Meta().MaxTime {
-			return errors.Errorf("block time ranges overlap", b.Meta().MinTime, prev.Meta().MaxTime)
+			return errors.Errorf("block time ranges overlap (%d, %d)", b.Meta().MinTime, prev.Meta().MaxTime)
 		}
 	}
 	return nil
@@ -480,6 +523,8 @@ func (db *DB) Close() error {
 
 // Appender returns a new Appender on the database.
 func (db *DB) Appender() Appender {
+	db.metrics.activeAppenders.Inc()
+
 	db.mtx.RLock()
 	return &dbAppender{db: db}
 }
@@ -619,6 +664,7 @@ func (db *DB) ensureHead(t int64) error {
 }
 
 func (a *dbAppender) Commit() error {
+	defer a.db.metrics.activeAppenders.Dec()
 	defer a.db.mtx.RUnlock()
 
 	// Commits to partial appenders must be concurrent as concurrent appenders
@@ -649,6 +695,7 @@ func (a *dbAppender) Commit() error {
 }
 
 func (a *dbAppender) Rollback() error {
+	defer a.db.metrics.activeAppenders.Dec()
 	defer a.db.mtx.RUnlock()
 
 	var g errgroup.Group