diff --git a/storage/src/main/java/org/zstack/storage/snapshot/VolumeSnapshotTreeBase.java b/storage/src/main/java/org/zstack/storage/snapshot/VolumeSnapshotTreeBase.java
index beb8b044d1a..f3195668f4b 100755
--- a/storage/src/main/java/org/zstack/storage/snapshot/VolumeSnapshotTreeBase.java
+++ b/storage/src/main/java/org/zstack/storage/snapshot/VolumeSnapshotTreeBase.java
@@ -884,8 +884,8 @@ private void stepDelete(Completion completion) {
                     return;
                 }
 
-                VolumeTree.VolumeSnapshotLeaf onlineChild = children.stream()
-                        .filter(child -> volumeTree.isOnline(current, currentRoot.getUuid(), child.getUuid(), vmState))
+                VolumeTree.VolumeSnapshotLeaf aliveChild = children.stream()
+                        .filter(child -> volumeTree.isOnAliveChain(child.getUuid()))
                         .findFirst().orElse(null);
 
                 Completion comp = new Completion(completion) {
@@ -910,7 +910,7 @@ public void fail(ErrorCode errorCode) {
                         pull(child, volumeTree, online, comp);
                     }
                 } else {
-                    if (onlineChild != null && Objects.equals(child.getUuid(), onlineChild.getUuid())) {
+                    if (aliveChild != null && Objects.equals(child.getUuid(), aliveChild.getUuid())) {
                         child = children.get(1);
                     }
                     boolean online = volumeTree.isOnline(current, currentRoot.getUuid(), child.getUuid(), vmState);
diff --git a/storage/src/main/java/org/zstack/storage/snapshot/VolumeTree.java b/storage/src/main/java/org/zstack/storage/snapshot/VolumeTree.java
index ea669fd6202..f7b9bcc0ba3 100644
--- a/storage/src/main/java/org/zstack/storage/snapshot/VolumeTree.java
+++ b/storage/src/main/java/org/zstack/storage/snapshot/VolumeTree.java
@@ -361,12 +361,19 @@ public List<String> getAliveChainSnapshotUuids() {
         return aliveChain.stream().map(VolumeSnapshotInventory::getUuid).collect(Collectors.toList());
     }
 
+    public boolean isOnAliveChain(String snapshotUuid) {
+        return current && getAliveChainSnapshotUuids().contains(snapshotUuid);
+    }
+
+    public static boolean isHypervisorOperation(VmInstanceState vmState) {
+        return vmState == VmInstanceState.Running || vmState == VmInstanceState.Paused;
+    }
+
     public DeleteVolumeSnapshotDirection resolveDirection(String targetSnapshotUuid, String childSnapshotUuid, String initialDirection,
                                                           boolean targetSnapshotIsLatest, VmInstanceState vmState) {
-        boolean online = (vmState == VmInstanceState.Running || vmState == VmInstanceState.Paused)
-                && getAliveChainSnapshotUuids().contains(targetSnapshotUuid) && getAliveChainSnapshotUuids().contains(childSnapshotUuid);
-
-        boolean shouldUseCommitStrategy = current && !targetSnapshotIsLatest && online;
+        boolean targetOnAliveChain = isOnAliveChain(targetSnapshotUuid);
+        boolean childOnAliveChain = isOnAliveChain(childSnapshotUuid);
+        boolean shouldUseCommitStrategy = current && !targetSnapshotIsLatest && targetOnAliveChain && childOnAliveChain;
 
         if (Objects.equals(initialDirection, DeleteVolumeSnapshotDirection.Pull.toString()) && shouldUseCommitStrategy) {
             throw new IllegalArgumentException("the snapshot will be deleted by block 'commit', but the direction is 'pull', " +
@@ -387,8 +394,10 @@ public DeleteVolumeSnapshotDirection resolveDirection(String targetSnapshotUuid,
     }
 
     public boolean isOnline(boolean treeIsCurrent, String targetSnapshotUuid, String childSnapshotUuid, VmInstanceState vmState) {
-        return treeIsCurrent && (vmState == VmInstanceState.Running || vmState == VmInstanceState.Paused)
-                && getAliveChainSnapshotUuids().contains(targetSnapshotUuid) && getAliveChainSnapshotUuids().contains(childSnapshotUuid);
+        return treeIsCurrent
+                && isHypervisorOperation(vmState)
+                && getAliveChainSnapshotUuids().contains(targetSnapshotUuid)
+                && getAliveChainSnapshotUuids().contains(childSnapshotUuid);
     }
 
     // TODO(clone) : When both chain cloning and single-node snapshot deletion are enabled,