diff --git a/configs/milvus.yaml b/configs/milvus.yaml
index 7130608525f0e..dce2dcd98cea4 100644
--- a/configs/milvus.yaml
+++ b/configs/milvus.yaml
@@ -346,8 +346,8 @@ queryNode:
   mmap:
     mmapEnabled: false # Enable mmap for loading data
     growingMmapEnabled: false # Enable mmap for growing segment
-    fixedFileSizeForMmapAlloc: 4 #MB, fixed file size for mmap chunk manager to store chunk data
-    maxDiskUsagePercentageForMmapAlloc: 20 # max percentage of disk usage in memory mapping
+    fixedFileSizeForMmapAlloc: 1 #MB, fixed file size for mmap chunk manager to store chunk data
+    maxDiskUsagePercentageForMmapAlloc: 50 # max percentage of disk usage in memory mapping
   lazyload:
     enabled: false # Enable lazyload for loading data
     waitTimeout: 30000 # max wait timeout duration in milliseconds before start to do lazyload search and retrieve
diff --git a/internal/util/initcore/init_core.go b/internal/util/initcore/init_core.go
index 86d707161391d..a281d46a9dbfa 100644
--- a/internal/util/initcore/init_core.go
+++ b/internal/util/initcore/init_core.go
@@ -186,7 +186,7 @@ func InitMmapManager(params *paramtable.ComponentParam) error {
 	defer C.free(unsafe.Pointer(cCacheReadAheadPolicy))
 	diskCapacity := params.QueryNodeCfg.DiskCapacityLimit.GetAsUint64()
 	diskLimit := uint64(float64(params.QueryNodeCfg.MaxMmapDiskPercentageForMmapManager.GetAsUint64()*diskCapacity) * 0.01)
-	mmapFileSize := params.QueryNodeCfg.FixedFileSizeForMmapManager.GetAsUint64() * 1024 * 1024
+	mmapFileSize := params.QueryNodeCfg.FixedFileSizeForMmapManager.GetAsFloat() * 1024 * 1024
 	mmapConfig := C.CMmapConfig{
 		cache_read_ahead_policy: cCacheReadAheadPolicy,
 		mmap_path:               cMmapChunkManagerDir,