diff --git a/conf/db/upgrade/V4.10.20__schema.sql b/conf/db/upgrade/V4.10.20__schema.sql
index 6159313b0c..8ec59cd0ed 100644
--- a/conf/db/upgrade/V4.10.20__schema.sql
+++ b/conf/db/upgrade/V4.10.20__schema.sql
@@ -26,9 +26,12 @@ WHERE t.current = true
   AND v.rootImageUuid IS NOT NULL
   AND t.rootImageUuid IS NULL;
 
+
 DELETE ref FROM `zstack`.`VolumeSnapshotReferenceVO` ref
                     INNER JOIN `zstack`.`VolumeEO` vol ON vol.uuid = ref.referenceVolumeUuid
 WHERE ref.referenceType = 'VolumeVO'
   AND ref.referenceVolumeUuid = ref.referenceUuid
   AND ref.referenceInstallUrl NOT LIKE CONCAT('%', SUBSTRING_INDEX(vol.installPath, '/', -1), '%');
 
+UPDATE `zstack`.`GlobalConfigVO` SET value="64", defaultValue="64" WHERE category="volumeSnapshot" AND name="incrementalSnapshot.maxNum" AND value > 120;
+
diff --git a/conf/globalConfig/snapshot.xml b/conf/globalConfig/snapshot.xml
index 7e0be2676e..fcfc393178 100755
--- a/conf/globalConfig/snapshot.xml
+++ b/conf/globalConfig/snapshot.xml
@@ -4,7 +4,7 @@
         <category>volumeSnapshot</category>
         <name>incrementalSnapshot.maxNum</name>
         <description>The length of a volume snapshot chain. When the lenght of a volume snapshot chain reaches this value, the next volume snapshot will be a full snapshot</description>
-        <defaultValue>128</defaultValue>
+        <defaultValue>64</defaultValue>
         <type>java.lang.Integer</type>
     </config>
 
diff --git a/storage/src/main/java/org/zstack/storage/snapshot/VolumeSnapshotGlobalConfig.java b/storage/src/main/java/org/zstack/storage/snapshot/VolumeSnapshotGlobalConfig.java
index 079481d6ee..9948dbdf73 100755
--- a/storage/src/main/java/org/zstack/storage/snapshot/VolumeSnapshotGlobalConfig.java
+++ b/storage/src/main/java/org/zstack/storage/snapshot/VolumeSnapshotGlobalConfig.java
@@ -11,7 +11,7 @@
 public class VolumeSnapshotGlobalConfig {
     public static final String CATEGORY = "volumeSnapshot";
 
-    @GlobalConfigValidation(numberGreaterThan = 0)
+    @GlobalConfigValidation(numberGreaterThan = 0, numberLessThan = 120)
     public static GlobalConfig MAX_INCREMENTAL_SNAPSHOT_NUM = new GlobalConfig(CATEGORY, "incrementalSnapshot.maxNum");
     @GlobalConfigValidation(numberGreaterThan = 0)
     public static GlobalConfig SNAPSHOT_DELETE_PARALLELISM_DEGREE = new GlobalConfig(CATEGORY, "delete.parallelismDegree");