diff --git a/app/vmstorage/main.go b/app/vmstorage/main.go
index 17ccf7fc8..6b2d7f340 100644
--- a/app/vmstorage/main.go
+++ b/app/vmstorage/main.go
@@ -30,6 +30,9 @@ var (
 	snapshotAuthKey   = flag.String("snapshotAuthKey", "", "authKey, which must be passed in query string to /snapshot* pages")
 	forceMergeAuthKey = flag.String("forceMergeAuthKey", "", "authKey, which must be passed in query string to /internal/force_merge pages")
 
+	finalMergeDelay = flag.Duration("finalMergeDelay", 30*time.Second, "The delay before starting final merge for per-month partition after no new data is ingested into it. "+
+		"Query speed and disk space usage is usually reduced after the final merge is complete. Too low delay for final merge may result in increased "+
+		"disk IO usage and CPU usage")
 	bigMergeConcurrency   = flag.Int("bigMergeConcurrency", 0, "The maximum number of CPU cores to use for big merges. Default value is used if set to 0")
 	smallMergeConcurrency = flag.Int("smallMergeConcurrency", 0, "The maximum number of CPU cores to use for small merges. Default value is used if set to 0")
 	minScrapeInterval     = flag.Duration("dedup.minScrapeInterval", 0, "Remove superflouos samples from time series if they are located closer to each other than this duration. "+
@@ -46,6 +49,7 @@ func main() {
 	cgroup.UpdateGOMAXPROCSToCPUQuota()
 
 	storage.SetMinScrapeIntervalForDeduplication(*minScrapeInterval)
+	storage.SetFinalMergeDelay(*finalMergeDelay)
 	storage.SetBigMergeWorkersCount(*bigMergeConcurrency)
 	storage.SetSmallMergeWorkersCount(*smallMergeConcurrency)
 
diff --git a/lib/storage/partition.go b/lib/storage/partition.go
index cefa70c70..f159c0b98 100644
--- a/lib/storage/partition.go
+++ b/lib/storage/partition.go
@@ -958,7 +958,7 @@ func (pt *partition) partsMerger(mergerFunc func(isFinal bool) error) error {
 		if !errors.Is(err, errNothingToMerge) {
 			return err
 		}
-		if fasttime.UnixTimestamp()-lastMergeTime > 30 {
+		if fasttime.UnixTimestamp()-lastMergeTime > finalMergeDelaySeconds {
 			// We have free time for merging into bigger parts.
 			// This should improve select performance.
 			lastMergeTime = fasttime.UnixTimestamp()
@@ -980,6 +980,19 @@ func (pt *partition) partsMerger(mergerFunc func(isFinal bool) error) error {
 	}
 }
 
+var finalMergeDelaySeconds = uint64(30)
+
+// SetFinalMergeDelay sets the delay before doing final merge for partitions without newly ingested data.
+//
+// This function may be called only before Storage initialization.
+func SetFinalMergeDelay(delay time.Duration) {
+	delaySeconds := int(delay.Seconds() + 0.5)
+	if delaySeconds <= 0 {
+		return
+	}
+	finalMergeDelaySeconds = uint64(delaySeconds)
+}
+
 func maxRowsByPath(path string) uint64 {
 	freeSpace := fs.MustGetFreeSpace(path)