VM Snapshot vs Backup: Key Differences Explained

You might be preparing to run a risky database schema update or a major OS patch. You want an undo button, something fast, convenient, and reliable.

A virtual machine (VM) snapshot often feels like a backup because it lets you roll a system back in time, but treating it as one is risky. In virtualized environments, confusing the two leads to avoidable performance problems and, in the worst cases, permanent data loss. Although both allow you to revert to an earlier state, they work in fundamentally different ways.

This article examines how VM snapshots and backups work, how they behave over time, and what each one can and cannot protect you from.

#What is the difference between a VM Snapshot and VM Backup?

A VM snapshot captures the state of a virtual machine at a specific point in time and depends on the original disk to function. A VM backup creates an independent copy of VM data for long-term storage, recovery, and protection against data loss, corruption, or system failure.

#What is a VM Snapshot?

A VM snapshot captures the state of a virtual machine at a specific moment, primarily to allow fast rollback after a change. Depending on how it is taken, that state may include the virtual disk alone or the disk and in-memory state. Snapshots are not full copies of a VM and are not intended for long-term retention.

Once a snapshot is created, the base virtual disk is frozen as read-only, and all subsequent writes are redirected to one or more delta files.

#How Do Snapshots Work?

When you take a snapshot, you are not creating a copy of the VM’s virtual disk. Instead, the hypervisor freezes the original virtual disk as read-only and creates a new delta or differencing disk. From that point forward, all new writes and changes are written to the delta disk, while the base disk remains untouched. This arrangement allows the VM’s disk state to be reverted to the point at which the snapshot was taken.

If you take additional snapshots, the process repeats, creating a chain of delta disks. Each delta disk depends on the one before it, forming a dependency chain that ultimately leads back to the original base disk.

A limitation of snapshots is this dependency on the base disk and underlying storage. Snapshots typically reside on the same datastore as the VM, so a failure of the primary storage system will destroy both the VM and all associated snapshots. Snapshots are effective for change control and testing, offering fast rollback, but they are not a substitute for an independent backup.

#Pros of Snapshots

• Creating a snapshot is fast, typically taking seconds to minutes, because no full data copy is created.

• Snapshots provide a reliable undo point. If a patch or configuration change breaks a system, you can revert to the snapshot and restore service quickly.

• Delta files start small and grow only as changes are written, making snapshots lightweight at creation time.

#Cons of Snapshots

• Snapshots are not independent; they depend entirely on the base disk. Losing the base disk means losing the snapshots.

• Snapshot chains degrade performance and increase storage usage as delta files grow over time.

#What is a VM Backup?

A VM backup is a complete, independent copy of a virtual machine’s data, stored separately from the source system. It typically includes the operating system, VM configuration, and application data, and is created specifically for recovery after data loss or infrastructure failure.

Unlike a snapshot, a backup does not depend on the original virtual disk or datastore. Once created, it can be used to restore the VM even if the original host, storage, or hypervisor is no longer available. This separation of fate is what makes backups suitable for disaster recovery, ransomware recovery, and long-term retention.

Many providers now offer managed VM backup services that implement these principles automatically. For example, Cherry Servers’ Automatic Backup Service creates daily point-in-time backups stored on separate infrastructure nodes, giving you genuine separation of fate and simplified recovery.

#How Do VM Backups Work?

A VM backup works by reading data directly from a virtual machine’s disks and copying it to a separate, isolated storage system. The data is transferred off the primary host and stored independently, so it can be used even if the original VM, datastore, or compute node is lost.

Backups may be stored on another server, dedicated network storage, cloud object storage, or archival media. Regardless of the destination, the defining requirement is separation of fate. The backup must not depend on the source VM’s disk files to restore.

Because backups are designed for long-term retention, they protect against hardware failure, storage corruption, ransomware, and data center-level incidents. Restoring from a backup is slower and more involved than reverting a snapshot, but it is the only reliable way to recover a VM after a catastrophic loss.

#Pros of Backups

• Backups are stored separately from the running VM. If a server, storage array, or even an entire data center is lost due to ransomware, fire, or hardware failure, the backup copy remains available.

• Backups support daily, weekly, and monthly retention policies, making them suitable for operational recovery as well as business and compliance requirements.

• A backup can be used to rebuild a VM without relying on snapshot chains or the original virtual disks.

• Backups are the only practical way to meet the industry-standard 3-2-1 rule: three copies of data, on two different media types, with at least one copy stored off-site.

#Cons of Backups

• Copying VM data to external storage takes time, ranging from minutes to hours, depending on data size and throughput.

• Full backups require storage capacity comparable to the size of the VM’s data especially for the initial full backup.

• Restoring from a backup involves copying data back into the VM, which is typically slower than reverting a snapshot.

#VM Snapshot vs. Backup

A snapshot is not a backup. The difference lies in architectural independence and the level of risk each tool is designed to mitigate.

The table below summarizes the key differences between VM snapshots and VM backups:

#When to use a Snapshot

• Before applying an operating system patch or software update

• Before installing a new application

• Before testing a configuration change

• When you intend to delete the snapshot within 24 to 72 hours after confirming the change was successful

#When to use a Backup

• To protect against hardware failure or storage corruption

• To recover from a ransomware attack

• To restore data that was deleted days or weeks earlier

• To meet long-term data retention or compliance requirements

• As the primary mechanism for daily data protection

• For all routine daily, weekly, and monthly recovery workflows

Never use snapshots as a substitute for backups.

#Conclusion

By now, the distinction should be clear. Snapshots and backups serve different roles. Snapshots provide a fast, temporary rollback point for operational changes and depend on the original VM and its storage. They are meant to be short-lived.

Backups create independent copies of VM data, stored separately and retained over time. This independence is what allows recovery after hardware failure, ransomware, or complete system loss.

Snapshots help undo recent changes. Backups make recovery possible after a loss. When each is used within its limits, they complement rather than replace one another.

Cherry Servers’ Automatic Backup Service provides daily automatic backups with a configurable backup window and manual recovery points. Backups are retained separately from your primary infrastructure and can be restored from the control panel for disaster recovery.