VMware Snapshot With Memory vs Quiesced Snapshot: What I Check Before Using Them

VMware snapshots are simple to create, but the options are often misunderstood. The two checkboxes that cause the most confusion are Snapshot the virtual machine’s memory and Quiesce guest file system.

Here is how I usually explain them during maintenance work.

Snapshot with memory

A memory snapshot captures the VM’s running memory state. When you revert, the VM comes back close to the state it was in when the snapshot was taken.

This can be useful before a risky application change, but it has tradeoffs:

• Snapshot creation can take longer.
• The VM may be stunned briefly.
• The snapshot consumes more datastore space.
• It is not always what you want for database or application consistency.

Quiesced snapshot

A quiesced snapshot asks VMware Tools and the guest OS to flush file system activity before the snapshot is taken. On Windows, this may involve VSS. On Linux, behavior depends on tools, file systems, and application support.

This option is more about guest file system consistency than preserving the running memory state.

Crash-consistent snapshot

If you do not select memory and do not quiesce, the snapshot is usually crash-consistent. That means it is similar to pulling power at that moment and later booting the VM from disk state.

For many simple workloads this is acceptable. For databases, domain controllers, or busy transactional systems, you should be more careful.

Which one should you choose?

• Before a quick OS patch: often no memory, maybe quiesce if supported.
• Before an application change where rollback to running state matters: consider memory snapshot.
• Before database changes: use application-aware backup or vendor procedure first.
• Before storage-heavy operations: avoid leaving snapshots open for long.

What I check before creating a snapshot

1. Datastore free space.
2. Existing snapshots.
3. VM disk size and write rate.
4. Whether VMware Tools is healthy.
5. Whether the workload is database-like.
6. How long the snapshot will exist.
7. Who will delete/consolidate it after the change.

Do not use snapshots as backups

A snapshot is not a backup. It depends on the base disk and the same datastore. If the datastore is lost, the snapshot does not save you. If a snapshot grows too much, it can hurt performance or fill the datastore.

Final note

For most maintenance work, the dangerous part is not creating a snapshot. The dangerous part is forgetting it. Always have an owner and a deletion time before creating one.