diff --git a/header/src/main/java/org/zstack/header/volume/MaxDataVolumeNumberExtensionPoint.java b/header/src/main/java/org/zstack/header/volume/MaxDataVolumeNumberExtensionPoint.java
index 36427bf6951..0ab65f307f2 100755
--- a/header/src/main/java/org/zstack/header/volume/MaxDataVolumeNumberExtensionPoint.java
+++ b/header/src/main/java/org/zstack/header/volume/MaxDataVolumeNumberExtensionPoint.java
@@ -6,4 +6,8 @@ public interface MaxDataVolumeNumberExtensionPoint {
     String getHypervisorTypeForMaxDataVolumeNumberExtension();
 
     int getMaxDataVolumeNumber();
+
+    default int getMaxDataVolumeNumberForRunningVm() {
+        return getMaxDataVolumeNumber();
+    }
 }
diff --git a/plugin/kvm/src/main/java/org/zstack/kvm/KVMConstant.java b/plugin/kvm/src/main/java/org/zstack/kvm/KVMConstant.java
index 1b2df9f8f2a..33ec5c90baa 100755
--- a/plugin/kvm/src/main/java/org/zstack/kvm/KVMConstant.java
+++ b/plugin/kvm/src/main/java/org/zstack/kvm/KVMConstant.java
@@ -160,6 +160,11 @@ public interface KVMConstant {
 
     Integer DEFAULT_MAX_NIC_QUEUE_NUMBER = 12;
 
+    // Maximum data volumes for hot-plug (running VM) due to PCI bus slot constraints.
+    // i440fx provides 32 PCI slots; ~12 are reserved by system devices and libvirt PCI bridge,
+    // leaving ~20 slots for hot-plugged virtio-blk data volumes (SharedBlock storage scenario).
+    int KVM_MAX_DATA_VOLUME_NUMBER_HOT_PLUG = 20;
+
     String CONNECT_HOST_PRIMARYSTORAGE_ERROR = "psError";
 
     String VIRTUALIZER_QEMU_KVM = "qemu-kvm";
diff --git a/plugin/kvm/src/main/java/org/zstack/kvm/KVMHostFactory.java b/plugin/kvm/src/main/java/org/zstack/kvm/KVMHostFactory.java
index 0188c920a83..2050e483abf 100755
--- a/plugin/kvm/src/main/java/org/zstack/kvm/KVMHostFactory.java
+++ b/plugin/kvm/src/main/java/org/zstack/kvm/KVMHostFactory.java
@@ -1098,6 +1098,11 @@ public int getMaxDataVolumeNumber() {
         return maxDataVolumeNum;
     }
 
+    @Override
+    public int getMaxDataVolumeNumberForRunningVm() {
+        return Math.min(maxDataVolumeNum, KVMConstant.KVM_MAX_DATA_VOLUME_NUMBER_HOT_PLUG);
+    }
+
     @Override
     @AsyncThread
     public void managementNodeReady() {
diff --git a/storage/src/main/java/org/zstack/storage/volume/VolumeBase.java b/storage/src/main/java/org/zstack/storage/volume/VolumeBase.java
index d75fb654a3e..2a81910337c 100755
--- a/storage/src/main/java/org/zstack/storage/volume/VolumeBase.java
+++ b/storage/src/main/java/org/zstack/storage/volume/VolumeBase.java
@@ -3272,7 +3272,10 @@ static void vmAttachVolumeValidator(VmInstanceInventory vmInv, String volumeUuid
 
         PluginRegistry pluginRgty = Platform.getComponentLoader().getComponent(PluginRegistry.class);
         MaxDataVolumeNumberExtensionPoint ext = pluginRgty.getExtensionFromMap(hypervisorType, MaxDataVolumeNumberExtensionPoint.class);
-        int maxDataVolumeNum = ext == null ? VolumeConstant.DEFAULT_MAX_DATA_VOLUME_NUMBER : ext.getMaxDataVolumeNumber();
+        boolean isRunning = VmInstanceState.Running.toString().equals(vmInv.getState())
+                || VmInstanceState.Paused.toString().equals(vmInv.getState());
+        int maxDataVolumeNum = ext == null ? VolumeConstant.DEFAULT_MAX_DATA_VOLUME_NUMBER
+                : (isRunning ? ext.getMaxDataVolumeNumberForRunningVm() : ext.getMaxDataVolumeNumber());
 
         long vmDataVolumeUsage = Q.New(VolumeVO.class)
                 .eq(VolumeVO_.type, VolumeType.Data)