feat(backups): use NBD to export VDIs when possible

@xen-orchestra/backups/Backup.js

@@ -43,6 +43,7 @@ const DEFAULT_VM_SETTINGS = {
   offlineSnapshot: false,
   snapshotRetention: 0,
   timeout: 0,
+  useNbd: false,
   unconditionalSnapshot: false,
   vmTimeout: 0,
 }

@xen-orchestra/backups/RemoteAdapter.js

@@ -659,9 +659,8 @@ class RemoteAdapter {
     return path
   }
 
-  async writeVhd(path, input, { checksum = true, validator = noop, writeBlockConcurrency } = {}) {
+  async writeVhd(path, input, { checksum = true, validator = noop, writeBlockConcurrency, nbdClient } = {}) {
     const handler = this._handler
-
     if (this.#useVhdDirectory()) {
       const dataPath = `${dirname(path)}/data/${uuidv4()}.vhd`
       await createVhdDirectoryFromStream(handler, dataPath, input, {
@@ -671,6 +670,7 @@ class RemoteAdapter {
           await input.task
           return validator.apply(this, arguments)
         },
+        nbdClient,
       })
       await VhdAbstract.createAlias(handler, path, dataPath)
     } else {

@xen-orchestra/backups/package.json

@@ -22,6 +22,7 @@
     "@vates/decorate-with": "^2.0.0",
     "@vates/disposable": "^0.1.2",
     "@vates/fuse-vhd": "^1.0.0",
+    "@vates/nbd-client": "*",
     "@vates/parse-duration": "^0.1.1",
     "@xen-orchestra/async-map": "^0.1.2",
     "@xen-orchestra/fs": "^3.2.0",

@xen-orchestra/backups/writers/DeltaBackupWriter.js

@@ -19,8 +19,9 @@ const { AbstractDeltaWriter } = require('./_AbstractDeltaWriter.js')
 const { checkVhd } = require('./_checkVhd.js')
 const { packUuid } = require('./_packUuid.js')
 const { Disposable } = require('promise-toolbox')
+const NbdClient = require('@vates/nbd-client')
 
-const { warn } = createLogger('xo:backups:DeltaBackupWriter')
+const { debug, warn } = createLogger('xo:backups:DeltaBackupWriter')
 
 exports.DeltaBackupWriter = class DeltaBackupWriter extends MixinBackupWriter(AbstractDeltaWriter) {
   async checkBaseVdis(baseUuidToSrcVdi) {
@@ -199,12 +200,30 @@ exports.DeltaBackupWriter = class DeltaBackupWriter extends MixinBackupWriter(Ab
             await checkVhd(handler, parentPath)
           }
 
+          const vdiRef = vm.$xapi.getObject(vdi.uuid).$ref
+
+          let nbdClient
+          if (!this._backup.config.useNbd) {
+            // get nbd if possible
+            try {
+              // this will always take the first host in the list
+              const [nbdInfo] = await vm.$xapi.call('VDI.get_nbd_info', vdiRef)
+              nbdClient = new NbdClient(nbdInfo)
+              await nbdClient.connect()
+              debug(`got nbd connection `, { vdi: vdi.uuid })
+            } catch (error) {
+              nbdClient = undefined
+              debug(`can't connect to nbd server or no server available`, { error })
+            }
+          }
+
           await adapter.writeVhd(path, deltaExport.streams[`${id}.vhd`], {
             // no checksum for VHDs, because they will be invalidated by
             // merges and chainings
             checksum: false,
             validator: tmpPath => checkVhd(handler, tmpPath),
             writeBlockConcurrency: this._backup.config.writeBlockConcurrency,
+            nbdClient,
           })
 
           if (isDelta) {

CHANGELOG.unreleased.md

@@ -7,6 +7,8 @@
 
 > Users must be able to say: “Nice enhancement, I'm eager to test it”
 
+- [Delta Backup] Use [NBD](https://en.wikipedia.org/wiki/Network_block_device) to download disks (PR [#6461](https://github.com/vatesfr/xen-orchestra/pull/6461))
+
 ### Bug fixes
 
 > Users must be able to say: “I had this issue, happy to know it's fixed”
@@ -27,4 +29,7 @@
 
 <!--packages-start-->
 
+- xo-server minor
+- xo-web minor
+
 <!--packages-end-->

packages/vhd-lib/createVhdDirectoryFromStream.js

@@ -8,10 +8,10 @@ const { asyncEach } = require('@vates/async-each')
 
 const { warn } = createLogger('vhd-lib:createVhdDirectoryFromStream')
 
-const buildVhd = Disposable.wrap(async function* (handler, path, inputStream, { concurrency, compression }) {
+const buildVhd = Disposable.wrap(async function* (handler, path, inputStream, { concurrency, compression, nbdClient }) {
   const vhd = yield VhdDirectory.create(handler, path, { compression })
   await asyncEach(
-    parseVhdStream(inputStream),
+    parseVhdStream(inputStream, nbdClient),
     async function (item) {
       switch (item.type) {
         case 'footer':
@@ -44,10 +44,10 @@ exports.createVhdDirectoryFromStream = async function createVhdDirectoryFromStre
   handler,
   path,
   inputStream,
-  { validator, concurrency = 16, compression } = {}
+  { validator, concurrency = 16, compression, nbdClient } = {}
 ) {
   try {
-    await buildVhd(handler, path, inputStream, { concurrency, compression })
+    await buildVhd(handler, path, inputStream, { concurrency, compression, nbdClient })
     if (validator !== undefined) {
       await validator.call(this, path)
     }