diff --git a/packages/xo-server/package.json b/packages/xo-server/package.json
index f43596038..4890411ea 100644
--- a/packages/xo-server/package.json
+++ b/packages/xo-server/package.json
@@ -69,6 +69,7 @@
     "http-server-plus": "^0.9.0",
     "human-format": "^0.10.0",
     "is-redirect": "^1.0.0",
+    "jest-worker": "^22.4.3",
     "js-yaml": "^3.10.0",
     "json-rpc-peer": "^0.15.3",
     "json5": "^1.0.0",
diff --git a/packages/xo-server/src/remote-handlers/index.js b/packages/xo-server/src/remote-handlers/index.js
new file mode 100644
index 000000000..c43db88a2
--- /dev/null
+++ b/packages/xo-server/src/remote-handlers/index.js
@@ -0,0 +1,25 @@
+// @flow
+
+import type RemoteHandler from './abstract'
+import RemoteHandlerLocal from './local'
+import RemoteHandlerNfs from './nfs'
+import RemoteHandlerSmb from './smb'
+
+export type Remote = { url: string }
+
+const HANDLERS = {
+  file: RemoteHandlerLocal,
+  smb: RemoteHandlerSmb,
+  nfs: RemoteHandlerNfs,
+}
+
+export const getHandler = (remote: Remote): RemoteHandler => {
+  // FIXME: should be done in xo-remote-parser.
+  const type = remote.url.split('://')[0]
+
+  const Handler = HANDLERS[type]
+  if (!Handler) {
+    throw new Error('Unhandled remote type')
+  }
+  return new Handler(remote)
+}
diff --git a/packages/xo-server/src/xo-mixins/backups-ng/index.js b/packages/xo-server/src/xo-mixins/backups-ng/index.js
index cf59d8ce9..d9fb0418b 100644
--- a/packages/xo-server/src/xo-mixins/backups-ng/index.js
+++ b/packages/xo-server/src/xo-mixins/backups-ng/index.js
@@ -25,7 +25,7 @@ import {
   safeDateFormat,
   serializeError,
 } from '../../utils'
-import mergeVhd, {
+import {
   chainVhd,
   createReadStream as createVhdReadStream,
   readVhdMetadata,
@@ -308,6 +308,7 @@ export default class BackupNg {
     getJob: (id: string, 'backup') => Promise<BackupJob>,
     updateJob: ($Shape<BackupJob>) => Promise<BackupJob>,
     removeJob: (id: string) => Promise<void>,
+    worker: $Dict<any>,
   }
 
   constructor (app: any) {
@@ -1044,7 +1045,12 @@ export default class BackupNg {
     $defer.onFailure.call(handler, 'unlink', path)
 
     const childPath = child.path
-    await mergeVhd(handler, path, handler, childPath)
+    await this._app.worker.mergeVhd(
+      handler._remote,
+      path,
+      handler._remote,
+      childPath
+    )
     await handler.rename(path, childPath)
   }
 
diff --git a/packages/xo-server/src/xo-mixins/remotes.js b/packages/xo-server/src/xo-mixins/remotes.js
index 82f576007..460cc36d4 100644
--- a/packages/xo-server/src/xo-mixins/remotes.js
+++ b/packages/xo-server/src/xo-mixins/remotes.js
@@ -1,9 +1,7 @@
 import { noSuchObject } from 'xo-common/api-errors'
 
-import RemoteHandlerLocal from '../remote-handlers/local'
-import RemoteHandlerNfs from '../remote-handlers/nfs'
-import RemoteHandlerSmb from '../remote-handlers/smb'
 import { forEach, mapToArray } from '../utils'
+import { getHandler } from '../remote-handlers'
 import { Remotes } from '../models/remote'
 
 // ===================================================================
@@ -40,20 +38,7 @@ export default class {
       throw new Error('remote is disabled')
     }
 
-    const HANDLERS = {
-      file: RemoteHandlerLocal,
-      smb: RemoteHandlerSmb,
-      nfs: RemoteHandlerNfs,
-    }
-
-    // FIXME: should be done in xo-remote-parser.
-    const type = remote.url.split('://')[0]
-
-    const Handler = HANDLERS[type]
-    if (!Handler) {
-      throw new Error('Unhandled remote type')
-    }
-    return new Handler(remote)
+    return getHandler(remote)
   }
 
   async testRemote (remote) {
diff --git a/packages/xo-server/src/xo-mixins/workers/index.js b/packages/xo-server/src/xo-mixins/workers/index.js
new file mode 100644
index 000000000..801c6f205
--- /dev/null
+++ b/packages/xo-server/src/xo-mixins/workers/index.js
@@ -0,0 +1,14 @@
+import Worker from 'jest-worker'
+
+export default class Workers {
+  get worker () {
+    return this._worker
+  }
+
+  constructor (app) {
+    app.on('start', () => {
+      this._worker = new Worker(require.resolve('./worker'))
+    })
+    app.on('stop', () => this._worker.end())
+  }
+}
diff --git a/packages/xo-server/src/xo-mixins/workers/worker.js b/packages/xo-server/src/xo-mixins/workers/worker.js
new file mode 100644
index 000000000..a86688793
--- /dev/null
+++ b/packages/xo-server/src/xo-mixins/workers/worker.js
@@ -0,0 +1,18 @@
+// @flow
+
+import mergeVhd_ from '../../vhd-merge'
+import { type Remote, getHandler } from '../../remote-handlers'
+
+export function mergeVhd (
+  parentRemote: Remote,
+  parentPath: string,
+  childRemote: Remote,
+  childPath: string
+) {
+  return mergeVhd_(
+    getHandler(parentRemote),
+    parentPath,
+    getHandler(childRemote),
+    childPath
+  )
+}
diff --git a/yarn.lock b/yarn.lock
index 09aa5ddcc..9466bbb6e 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -4313,7 +4313,7 @@ eslint@^4.14.0:
     doctrine "^2.1.0"
     eslint-scope "^3.7.1"
     eslint-visitor-keys "^1.0.0"
-    espree "^3.5.4"
+    espree "^3.5.2"
     esquery "^1.0.0"
     esutils "^2.0.2"
     file-entry-cache "^2.0.0"
@@ -4335,7 +4335,6 @@ eslint@^4.14.0:
     path-is-inside "^1.0.2"
     pluralize "^7.0.0"
     progress "^2.0.0"
-    regexpp "^1.0.1"
     require-uncached "^1.0.3"
     semver "^5.3.0"
     strip-ansi "^4.0.0"
@@ -4343,7 +4342,7 @@ eslint@^4.14.0:
     table "4.0.2"
     text-table "~0.2.0"
 
-espree@^3.5.4:
+espree@^3.5.2:
   version "3.5.4"
   resolved "https://registry.yarnpkg.com/espree/-/espree-3.5.4.tgz#b0f447187c8a8bed944b815a660bddf5deb5d1a7"
   dependencies:
@@ -6769,6 +6768,12 @@ jest-worker@^22.2.2:
   dependencies:
     merge-stream "^1.0.1"
 
+jest-worker@^22.4.3:
+  version "22.4.3"
+  resolved "https://registry.yarnpkg.com/jest-worker/-/jest-worker-22.4.3.tgz#5c421417cba1c0abf64bf56bd5fb7968d79dd40b"
+  dependencies:
+    merge-stream "^1.0.1"
+
 jest@^22.0.4:
   version "22.4.2"
   resolved "https://registry.yarnpkg.com/jest/-/jest-22.4.2.tgz#34012834a49bf1bdd3bc783850ab44e4499afc20"
@@ -9913,10 +9918,6 @@ regex-not@^1.0.0, regex-not@^1.0.2:
     extend-shallow "^3.0.2"
     safe-regex "^1.1.0"
 
-regexpp@^1.0.1:
-  version "1.0.1"
-  resolved "https://registry.yarnpkg.com/regexpp/-/regexpp-1.0.1.tgz#d857c3a741dce075c2848dcb019a0a975b190d43"
-
 regexpu-core@^2.0.0:
   version "2.0.0"
   resolved "https://registry.yarnpkg.com/regexpu-core/-/regexpu-core-2.0.0.tgz#49d038837b8dcf8bfa5b9a42139938e6ea2ae240"