fix(backups): failing replication of qcow2 disks (#10319)

* fix(backups):  task label NBT->NBD

* fix: still force a list block only call for NBD + stream scenario , that was failing to transfer disk on fallback

@xen-orchestra/backups/_runners/_writers/IncrementalXapiWriter.mjs

@@ -263,6 +263,7 @@ export class IncrementalXapiWriter extends MixinXapiWriter(AbstractIncrementalWr
             vdiRef: activeVdi.$ref,
             baseRef: snapshot.$ref,
             onlyListChangedBlocks: true,
+            preferNbd: this._settings.preferNbd,
           })
           await diffDisk.init()
           if (diffDisk.getBlockIndexes().length === 0) {

@xen-orchestra/xapi/disks/Xapi.mjs

@@ -98,6 +98,7 @@ export class XapiDiskSource extends DiskPassthrough {
     let source
     let streamSource
     try {
+      // we will only use the stream for bloc list
       streamSource = await this.#openExportStream({ onlyListChangedBlocks: true })
       if (streamSource === undefined) {
         throw new Error(`Can't open stream source`)
@@ -111,7 +112,7 @@ export class XapiDiskSource extends DiskPassthrough {
       await source.init()
       this.#useNbd = true
 
-      return await this.#formatSourceDisk(source, 'NBT')
+      return await this.#formatSourceDisk(source, 'NBD')
     } catch (err) {
       // init probaby failed, so nothing to close , but better safe than sorry
       await source?.close().catch(warn)
@@ -163,7 +164,7 @@ export class XapiDiskSource extends DiskPassthrough {
    *
    * @returns {Promise<Disk>}
    */
-  async #openExportStream({ onlyListChangedBlocks = false } = {}) {
+  async #openExportStream({ onlyListChangedBlocks = this.#onlyListChangedBlocks } = {}) {
     const xapi = this.#xapi
     const baseRef = this.#baseRef
     const vdiRef = this.#vdiRef
@@ -263,7 +264,7 @@ export class XapiDiskSource extends DiskPassthrough {
       await source.init()
       this.#useNbd = true
       this.#useCbt = true
-      return await this.#formatSourceDisk(source, 'NBT+CBT')
+      return await this.#formatSourceDisk(source, 'NBD+CBT')
     } catch (error) {
       if (/** @type {NodeJS.ErrnoException} */ (error).code !== 'CBT_DISABLED') {
         info('Error in openNbdCBT', error)

CHANGELOG.unreleased.md

@@ -17,6 +17,8 @@
 
 > Users must be able to say: "I had this issue, happy to know it's fixed"
 
+- [Backups] Fix slow replication startup and fallback to full on qcow2 (PR [#10319](https://github.com/vatesfr/xen-orchestra/pull/10319))
+
 ### Packages to release
 
 > When modifying a package, add it here with its release type.
@@ -33,4 +35,6 @@
 
 <!--packages-start-->
 
+- @xen-orchestra/backups patch
+- @xen-orchestra/xapi patch
 <!--packages-end-->