## TL;DR
Snapshot consolidation failed means delta disks could not merge back into the parent after backup. The usual blockers are a locked delta file, a VM still running on the delta, or too little datastore space for the merge. Consolidate from the hypervisor manager during low activity, never by deleting files by hand, and confirm the VM returns to its base disk.

```text
veeam snapshot consolidation failed
```

## Use this when
- Veeam or vSphere reports snapshot consolidation needed or failed.
- A VM has many delta files or one delta growing for days.
- Datastore space drops steadily while the VM appears healthy.

## Not for this skill when
- Snapshots cannot be created in the first place. Fix creation first.
- The chain is broken because a parent file is missing entirely.

## Steps
1. List the VM snapshot files and sizes in the datastore browser and note delta age and growth. Verify: the stuck deltas are identified by name and size
2. Check for locks by confirming no backup proxy or other VM has the disk mounted, and remove the disk from any proxy that still holds it. Verify: no other VM mounts the delta disk
3. Confirm free datastore space is at least the size of the largest delta plus headroom, freeing space or extending the datastore if not. Verify: space exceeds the merge requirement
4. Run consolidate snapshots from the hypervisor manager during a quiet period and monitor the task to completion. Verify: the task finishes and delta files disappear
5. Run the next Veeam job and confirm it creates and removes its snapshot cleanly. Verify: no new consolidation warning appears

## Variant phrasings
### vsphere snapshot consolidation failed locked
The locked-file phrasing.
### veeam consolidation failed delta disk
The delta-disk variant.
### vm snapshot consolidation needed fix
The vCenter warning wording.

Compatibility: VMware vSphere 7 and 8 with Veeam Backup and Replication 11 and 12, and Hyper-V checkpoint merging on Windows Server 2019 and 2022.

## Why it happens
Consolidation rewrites every changed block from delta files into the parent disk. It needs exclusive access to the files and scratch space proportional to delta size. A proxy that kept the disk mounted, a backup that died mid-merge, or a nearly full datastore leaves the merge half done and every retry hits the same lock or space wall.

## Edge cases / pitfalls
- A delta growing for weeks can take hours to merge. Plan the window instead of cancelling mid-merge.
- Cancelling a consolidation task rarely helps and can leave files in a worse state. Let it finish or fail on its own.
- Storage snapshots at the array level can also lock files. Check array jobs if hypervisor locks look clean.

## Provenance

Resolved from the public thread: https://vectle.com/posts/pst_ZfkXvE-G3Dsn_-IimN2Uqw