diff --git a/src/api/sr.js b/src/api/sr.js
index 2c933d4d5..7548e1d0c 100644
--- a/src/api/sr.js
+++ b/src/api/sr.js
@@ -817,3 +817,17 @@ reattachIso.params = {
 reattachIso.resolve = {
   host: ['host', 'host', 'administrate']
 }
+
+// -------------------------------------------------------------------
+
+export function getUnhealthyVdiChainsLength ({ sr }) {
+  return this.getXapi(sr).getUnhealthyVdiChainsLength(sr)
+}
+
+getUnhealthyVdiChainsLength.params = {
+  id: { type: 'string' }
+}
+
+getUnhealthyVdiChainsLength.resolve = {
+  sr: ['id', 'SR', 'operate']
+}
diff --git a/src/xapi/index.js b/src/xapi/index.js
index c2a8d07b3..5bfa79934 100644
--- a/src/xapi/index.js
+++ b/src/xapi/index.js
@@ -739,14 +739,16 @@ export default class Xapi extends XapiBase {
     return promise
   }
 
-  _assertHealthyVdiChain (vdi, childrenMap) {
+  _assertHealthyVdiChain (vdi, cache) {
     if (vdi == null) {
       return
     }
 
     if (!vdi.managed) {
+      const { SR } = vdi
+      let childrenMap = cache[SR]
       if (childrenMap === undefined) {
-        childrenMap = groupBy(vdi.$SR.$VDIs, _ => _.sm_config['vhd-parent'])
+        childrenMap = cache[SR] = groupBy(vdi.$SR.$VDIs, _ => _.sm_config['vhd-parent'])
       }
 
       // an unmanaged VDI should not have exactly one child: they
@@ -762,13 +764,14 @@ export default class Xapi extends XapiBase {
 
     this._assertHealthyVdiChain(
       this.getObjectByUuid(vdi.sm_config['vhd-parent'], null),
-      childrenMap
+      cache
     )
   }
 
   _assertHealthyVdiChains (vm) {
+    const cache = createRawObject()
     forEach(vm.$VBDs, ({ $VDI }) => {
-      this._assertHealthyVdiChain($VDI)
+      this._assertHealthyVdiChain($VDI, cache)
     })
   }
 
diff --git a/src/xapi/mixins/storage.js b/src/xapi/mixins/storage.js
index f6b863d30..a9c4155dd 100644
--- a/src/xapi/mixins/storage.js
+++ b/src/xapi/mixins/storage.js
@@ -1,4 +1,10 @@
 import {
+  forEach,
+  groupBy
+} from 'lodash'
+
+import {
+  createRawObject,
   mapToArray
 } from '../../utils'
 
@@ -49,5 +55,38 @@ export default {
 
   async unplugPbd (id) {
     await this._unplugPbd(this.getObject(id))
+  },
+
+  _getUnhealthyVdiChainLength (uuid, childrenMap, cache) {
+    let length = cache[uuid]
+    if (length === undefined) {
+      const children = childrenMap[uuid]
+      length = children !== undefined && children.length === 1
+        ? 1
+        : 0
+      const parent = this.getObjectByUuid(uuid).sm_config['vhd-parent']
+      if (parent !== undefined) {
+        length += this._getUnhealthyVdiChainLength(parent, childrenMap, cache)
+      }
+      cache[uuid] = length
+    }
+    return length
+  },
+
+  getUnhealthyVdiChainsLength (sr) {
+    const vdis = this.getObject(sr).$VDIs
+    const unhealthyVdis = createRawObject()
+    const children = groupBy(vdis, 'sm_config.vhd-parent')
+    const cache = createRawObject()
+    forEach(vdis, vdi => {
+      if (vdi.managed && !vdi.is_a_snapshot) {
+        const { uuid } = vdi
+        const length = this._getUnhealthyVdiChainLength(uuid, children, cache)
+        if (length !== 0) {
+          unhealthyVdis[uuid] = length
+        }
+      }
+    })
+    return unhealthyVdis
   }
 }