When it comes to protecting virtual machines, two common methods are taking snapshots and performing backups. While both of these techniques can be used to protect your data, they have different use cases and limitations.
In this blog post, we’ll explore the differences between VM snapshots and backups, their benefits and drawbacks, and when to use each method to ensure the safety and availability of your virtualized infrastructure.
What is Snapshot?
A VM snapshot is a point-in-time copy of a virtual machine’s state, including its memory, disk, and settings. It captures the VM’s current configuration and data, allowing you to revert the VM to that exact state at any time.
Snapshot Use Cases
It is used mostly during development or testing operations and software updates to roll back to the previous state if something goes wrong.
VMware Snapshot – An Overview
What is VMware Snapshot?
VMware Snapshot is a feature of VMware vSphere virtualization platform that allows you to take a point-in-time image of a virtual machine’s state, including its memory, disk, and settings.
How VMware Snapshot works?
When you take a snapshot of a VM in VMware, it captures the VM’s current state and saves it as a new point-in-time image. It records the state of the base virtual disk rather than a complete copy of the base disk; thus, we can only recover the data and not the entire VM.
The base disk is marked to read-only mode. A .vmdk child or delta disk is created where the changes made after the snapshots are monitored with the Changed Block Tracking Technology and stores only changes. Along with the child disk, two other disks are created. The.vmsd file is a database file that contains metadata and has connections to the following snapshots: .vmsn file, which collects the runtime information of the VM. Snapshots are stored in hierarchies based on the time they were taken. The first snapshot is an exact image of your machine, and the subsequent snapshots collect only the changed data blocks.
On restoring the snapshot, we return the virtual machine’s memory, settings, and the state of the virtual machine disks at the point of the snapshot. As the base disk is not copied completely and the dependency on the source file, makes the snapshot incapable of restoring a VM in case of storage failure.
The power state (ON/OFF) of the VM does not have any effect on the snapshots taken. It is recommended to retain a minimum number of snapshots (recommended < 32) for 2-3 days considering the storage consumption as it may affect the production servers. Learn more about VMware Snapshots and its best practices
Hyper-V Checkpoint – An Overview
What is Hyper-V Checkpoint?
Hyper-V Checkpoint allows you to take a point-in-time image of a virtual machine’s state, including its memory, disk, and settings, and store it as a checkpoint.
Hyper-V Checkpoint, formerly known as Hyper-V Snapshot, is a feature of the Hyper-V virtualization platform in Windows Server. It is similar as VMware snapshot.
How Hyper-V Checkpoint work?
When you take a checkpoint of a VM in Hyper-V, it captures the VM’s current state and saves it as a new point-in-time image. Any changes made to the VM after the checkpoint is taken are saved in a differencing disk, which is separate from the original VM disk. This differencing disk grows as more changes are made to the VM, but it does not affect the original VM disk. In detail, the basic disk is set to read-only mode and .avhd file is created to store VM changes. The other binary files that are created in the basic disk location are .vmcx to manage virtual machine configuration information and .vmrs to store runtime state information.
Learn more about the types of Hyper-V checkpoints, how they work, how to use and manage them here.
Pros of VM Snapshot
- Easy rollback: If something goes wrong after making changes to the VM, you can easily revert to the snapshot
- Testing and development: Snapshots can be used to create a backup of a VM before making changes or experimenting with different configurations or software versions. This allows developers to test new software or configurations without affecting the production environment
Cons of VM Snapshot
- Data loss: Snapshots are restricted to being stored on the same system’s storage. This implies that you run the chance of losing your snapshots if something goes wrong with the system has many snapshots
- Performance Impact: Slower VM performance and longer wait times for users if a virtual machine
- Increased storage usage: Increased storage usage: Snapshots can take up a lot of storage space, especially if they are kept for a long time or if changes are made frequently to the VM
Snapshots are not backups: Why snapshots alone are not enough to protect your VMs?
While snapshots can be a useful tool for backing up virtual machines, they are not a complete backup solution. Snapshots are dependent on the VM’s storage. If the storage is not available due to any case, then you will not be able to restore your VMs with snapshots. Also, Snapshots do not provide the same level of protection as regular backups because they only capture a point-in-time image of the VM, and do not necessarily include all data needed for a complete restore. It’s very important to prioritize VM backup over VM Snapshot because backups are necessary to keep your business running.
What is Backup?
A backup is a copy of the data (be a file or a complete machine) that can be stored in various storage targets (local storage, network storage, offsite) on any location (local/remote/cloud). The backup keeps your data always available and your data can be restored in cases of any data loss or a disaster.
Backups can be created in various ways, including manual copying of files to an external hard drive or cloud storage, or through automated backup software that creates backups on a regular schedule. Backups can be full, where all data is copied, or incremental, where only changes since the last backup are copied.
Reasons why backups are preferred over snapshots for data protection
Backups are preferred over snapshots for data protection because backups provide more reliable and comprehensive data protection.
- Backups create a copy of all data, whereas snapshots only capture the data that has changed since the last snapshot
- Snapshots are dependent on the source data and have a limited retention time due to memory consumption, whereas backups can be compressed and stored in local/offsite storage
- Backups allow for granular recovery and can restore data even if the primary storage location is deleted
- Backups are a better choice for long-term protection of digital assets, whereas snapshots are useful for short-term purposes like testing and development
Overall, backups provide more comprehensive and reliable data protection than snapshots.
VM Snapshot vs Backup – An Comparison
| Features | Snapshot | Backup |
|---|---|---|
| Data Location | Stored in the same location as the original data | Stored in another location (offsite storage, different drive, etc.) |
| Restoration | Relies on dependent files | Ability to restore even if primary storage is deleted |
| Granular | Granular recovery is not possible | Granular recovery is possible |
| Recovery Time | Quick process | Depends on the recovery option. Instant restores available to meet RTO < 5 mins |
| Retention Time | Limited to 24-72 hours due to memory consumption | Can be compressed and stored in on-premise/offsite storage |
| Usecase | For development and testing | Long-term protection of digital assets |
Conclusion:
In conclusion, while both VM snapshots and backups have their uses, snapshots are useful for short-term purposes, like testing and development, but backups are preferred for more reliable and comprehensive data protection. Therefore, it’s recommended to use snapshots in conjunction with regular backups to ensure the safety and availability of your virtualized infrastructure.
To ensure that your data is protected and backed up efficiently, it is important to use reliable backup software such as BDRSuite which is an excellent option for backing up your data.
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