diff --git a/internal/caches/storage_memory.go b/internal/caches/storage_memory.go
index 80ead0d..13e7dc5 100644
--- a/internal/caches/storage_memory.go
+++ b/internal/caches/storage_memory.go
@@ -485,7 +485,7 @@ func (this *MemoryStorage) startFlush() {
 			statCount = 0
 
 			// delay some time to reduce load if needed
-			if !fsutils.DiskIsFast {
+			if !fsutils.DiskIsFast() {
 				loadStat, err := load.Avg()
 				if err == nil && loadStat != nil {
 					if loadStat.Load1 > 10 {
diff --git a/internal/utils/fs/disk.go b/internal/utils/fs/disk.go
index c063cef..3d24551 100644
--- a/internal/utils/fs/disk.go
+++ b/internal/utils/fs/disk.go
@@ -64,11 +64,21 @@ func CheckDiskIsFast() (speedMB float64, isFast bool, err error) {
 	if err != nil {
 		return
 	}
-	isFast = speedMB > 120
+	isFast = speedMB > 150
+
+	if speedMB > 1000 {
+		DiskSpeed = SpeedExtremelyFast
+	} else if speedMB > 150 {
+		DiskSpeed = SpeedFast
+	} else if speedMB > 60 {
+		DiskSpeed = SpeedLow
+	} else {
+		DiskSpeed = SpeedExtremelySlow
+	}
+	calculateDiskMaxWrites()
 
 	if speedMB > DiskSpeedMB {
 		DiskSpeedMB = speedMB
-		DiskIsFast = isFast
 	}
 
 	return
diff --git a/internal/utils/fs/status.go b/internal/utils/fs/status.go
index 9d3302d..5b769b3 100644
--- a/internal/utils/fs/status.go
+++ b/internal/utils/fs/status.go
@@ -8,9 +8,33 @@ import (
 	"time"
 )
 
+type Speed int
+
+func (this Speed) String() string {
+	switch this {
+	case SpeedExtremelyFast:
+		return "extremely fast"
+	case SpeedFast:
+		return "fast"
+	case SpeedLow:
+		return "low"
+	case SpeedExtremelySlow:
+		return "extremely slow"
+	}
+	return "unknown"
+}
+
+const (
+	SpeedExtremelyFast Speed = 1
+	SpeedFast          Speed = 2
+	SpeedLow           Speed = 3
+	SpeedExtremelySlow Speed = 4
+)
+
 var (
-	DiskIsFast  bool
-	DiskSpeedMB float64
+	DiskSpeed           = SpeedLow
+	DiskMaxWrites int32 = 32
+	DiskSpeedMB   float64
 )
 
 func init() {
@@ -38,17 +62,14 @@ func init() {
 	}()
 }
 
+func DiskIsFast() bool {
+	return DiskSpeed == SpeedExtremelyFast || DiskSpeed == SpeedFast
+}
+
 var countWrites int32 = 0
 
-const MaxWrites = 32
-const MaxFastWrites = 128
-
 func WriteReady() bool {
-	var count = atomic.LoadInt32(&countWrites)
-	if DiskIsFast {
-		return count < MaxFastWrites
-	}
-	return count <= MaxWrites
+	return atomic.LoadInt32(&countWrites) < DiskMaxWrites
 }
 
 func WriteBegin() {
@@ -58,3 +79,18 @@ func WriteBegin() {
 func WriteEnd() {
 	atomic.AddInt32(&countWrites, -1)
 }
+
+func calculateDiskMaxWrites() {
+	switch DiskSpeed {
+	case SpeedExtremelyFast:
+		DiskMaxWrites = 256
+	case SpeedFast:
+		DiskMaxWrites = 128
+	case SpeedLow:
+		DiskMaxWrites = 32
+	case SpeedExtremelySlow:
+		DiskMaxWrites = 16
+	default:
+		DiskMaxWrites = 16
+	}
+}
diff --git a/internal/utils/fs/status_test.go b/internal/utils/fs/status_test.go
index c322984..2e30cff 100644
--- a/internal/utils/fs/status_test.go
+++ b/internal/utils/fs/status_test.go
@@ -11,7 +11,7 @@ import (
 func TestWrites(t *testing.T) {
 	var a = assert.NewAssertion(t)
 
-	for i := 0; i < fsutils.MaxWrites+1; i++ {
+	for i := 0; i < int(fsutils.DiskMaxWrites); i++ {
 		fsutils.WriteBegin()
 	}
 	a.IsFalse(fsutils.WriteReady())