diff --git a/packages/vhd-cli/src/commands/compare.js b/packages/vhd-cli/src/commands/compare.js
new file mode 100644
index 000000000..af3c85b78
--- /dev/null
+++ b/packages/vhd-cli/src/commands/compare.js
@@ -0,0 +1,81 @@
+import { getSyncedHandler } from '@xen-orchestra/fs'
+import { openVhd, Constants } from 'vhd-lib'
+import { resolve } from 'path'
+import Disposable from 'promise-toolbox/Disposable'
+import omit from 'lodash/omit'
+
+const deepCompareObjects = function (src, dest, path) {
+  for (const key of Object.keys(src)) {
+    const srcValue = src[key]
+    const destValue = dest[key]
+    if (srcValue !== destValue) {
+      const srcType = typeof srcValue
+      const destType = typeof destValue
+      if (srcType !== destType) {
+        throw new Error(`key ${path + '/' + key} is of type *${srcType}* in source and *${destType}* in dest`)
+      }
+
+      if (srcType !== 'object') {
+        throw new Error(`key ${path + '/' + key} is *${srcValue}* in source and *${destValue}* in dest`)
+      }
+
+      if (Buffer.isBuffer(srcValue)) {
+        if (!(Buffer.isBuffer(destValue) && srcValue.equals(destValue))) {
+          throw new Error(`key ${path + '/' + key} is buffer in source that does not equal dest`)
+        }
+      } else {
+        deepCompareObjects(src[key], dest[key], path + '/' + key)
+      }
+    }
+  }
+}
+
+export default async args => {
+  if (args.length < 2 || args.some(_ => _ === '-h' || _ === '--help')) {
+    return `Usage: compare <source VHD> <destination> `
+  }
+  const [sourcePath, destPath] = args
+
+  await Disposable.use(async function* () {
+    const handler = yield getSyncedHandler({ url: 'file:///' })
+    const src = yield openVhd(handler, resolve(sourcePath))
+    const dest = yield openVhd(handler, resolve(destPath))
+
+    // parent locator entries contains offset that can be different without impacting the vhd
+    // we'll compare them later
+    // table offset and checksum are also implementation specific
+    const ignoredEntries = ['checksum', 'parentLocatorEntry', 'tableOffset']
+    deepCompareObjects(omit(src.header, ignoredEntries), omit(dest.header, ignoredEntries), 'header')
+    deepCompareObjects(src.footer, dest.footer, 'footer')
+
+    await src.readBlockAllocationTable()
+    await dest.readBlockAllocationTable()
+
+    for (let i = 0; i < src.header.maxTableEntries; i++) {
+      if (src.containsBlock(i)) {
+        if (dest.containsBlock(i)) {
+          const srcBlock = await src.readBlock(i)
+          const destBlock = await dest.readBlock(i)
+
+          if (!srcBlock.buffer.equals(destBlock.buffer)) {
+            throw new Error(`Block  ${i} has different data in src and dest`)
+          }
+        } else {
+          throw new Error(`Block  ${i} is present in source but not in dest `)
+        }
+      } else if (dest.containsBlock(i)) {
+        throw new Error(`Block  ${i} is present in dest but not in source `)
+      }
+    }
+
+    for (let parentLocatorId = 0; parentLocatorId < Constants.PARENT_LOCATOR_ENTRIES; parentLocatorId++) {
+      const srcParentLocator = await src.readParentLocator(parentLocatorId)
+      const destParentLocator = await dest.readParentLocator(parentLocatorId)
+      if (!srcParentLocator.data || !srcParentLocator.data.equals(destParentLocator.data)) {
+        console.log(srcParentLocator, destParentLocator)
+        throw new Error(`Parent Locator  ${parentLocatorId} has different data in src and dest`)
+      }
+    }
+    console.log('there is no difference between theses vhd')
+  })
+}
diff --git a/packages/vhd-lib/src/Vhd/VhdFile.js b/packages/vhd-lib/src/Vhd/VhdFile.js
index 6bb0b3cab..72cea685b 100644
--- a/packages/vhd-lib/src/Vhd/VhdFile.js
+++ b/packages/vhd-lib/src/Vhd/VhdFile.js
@@ -54,7 +54,7 @@ export class VhdFile extends VhdAbstract {
   #uncheckedBlockTable
 
   get #blocktable() {
-    assert.notStrictEqual(this.#blockTable, undefined, 'Block table must be initialized before access')
+    assert.notStrictEqual(this.#uncheckedBlockTable, undefined, 'Block table must be initialized before access')
     return this.#uncheckedBlockTable
   }
 
diff --git a/packages/vhd-lib/src/index.js b/packages/vhd-lib/src/index.js
index fc94ce5ef..ec76498e8 100644
--- a/packages/vhd-lib/src/index.js
+++ b/packages/vhd-lib/src/index.js
@@ -8,5 +8,7 @@ export { default as createSyntheticStream } from './createSyntheticStream'
 export { default as createVhdStreamWithLength } from './createVhdStreamWithLength'
 export { default as mergeVhd } from './merge'
 export { default as peekFooterFromVhdStream } from './peekFooterFromVhdStream'
+export { openVhd } from './openVhd'
 export { VhdDirectory } from './Vhd/VhdDirectory'
 export { VhdFile } from './Vhd/VhdFile'
+export * as Constants from './_constants'
diff --git a/packages/vhd-lib/src/openVhd.js b/packages/vhd-lib/src/openVhd.js
new file mode 100644
index 000000000..3bfef44c0
--- /dev/null
+++ b/packages/vhd-lib/src/openVhd.js
@@ -0,0 +1,12 @@
+import { VhdFile, VhdDirectory } from './'
+
+export async function openVhd(handler, path) {
+  try {
+    return await VhdFile.open(handler, path)
+  } catch (e) {
+    if (e.code !== 'EISDIR') {
+      throw e
+    }
+    return await VhdDirectory.open(handler, path)
+  }
+}