A VM snapshot is a copy of a virtual machine (VM) at a specific point in time (PIT). It captures the VM’s data and state, including its memory, disk, and power. This enables administrators to perform a data rollback and revert to the previous state of the VM. VM snapshots are widely used in server virtualization to:
- Facilitate backup
- Manage rapid data rollback recovery
- Perform tests without affecting the original VM
How a VM Snapshot Works
Disk Snapshot
When you create a snapshot, the hypervisor (like VMware, Hyper-V, or Proxmox) stops writing data to the original virtual disk file (A). It creates a separate file (B) where all new data changes are stored. The original disk file (A) stays the same. If you revert to the snapshot (file A), the hypervisor deletes the new file (B) and restores the VM to its original state.
Memory Snapshot (Optional)
If you choose to include the VM’s memory in the snapshot, the hypervisor saves the entire RAM state.
Configuration Snapshot (Optional)
If you choose to, the hypervisor will also save the VM’s hardware settings (like CPU, RAM, and device configurations). This ensures the VM will run with the same hardware setup if you revert to the snapshot.
When to use a VM Snapshot
The VM snapshot feature is a fast, short-term solution for greater system protection. It’s used for managing and responding to system failures, software misconfigurations, data corruption, malware, or application errors. It’s particularly useful in development environments, where rapid testing and data rollback are common.
- Before Critical System Updates: You can use the snapshot feature before applying major software updates to quickly restore the system if the update causes issues.
- Configuration Changes: Create a snapshot before making major system configuration changes to easily roll back if the new settings cause problems.
- Testing New Applications: Use the snapshot feature to test new applications without affecting the current system state.
- Development and Testing Environments: Frequently create a snapshot in development environments to support rapid changes and testing.
- Troubleshooting System Issues: Take a snapshot before troubleshooting complex issues to quickly revert if the solution doesn’t work.
VM Snapshot vs. Backup
The VM snapshot feature is a powerful tool for short-term recovery, software testing, and minimizing downtime. However, it’s not a comprehensive alternative to backup solutions or long-term data protection.
This is because, unlike traditional backup, a VM snapshot does not create a complete copy. Instead, the feature is equivalent to taking a picture of your server at a specific moment in time. It’s made of data and some metadata that defines the state of your information, not a duplication of hard disk data.
Comprehensive, Traditional Backup
- Slower to create, better for long-term recovery
- Stored independently
- Creates a complete duplication of the entire system and files
- Designed for disaster recovery, compliance, and long-term data protection
VM Snapshot
- Fast to create and provides instant recovery access
- Relies on original VM storage
- Captures only data and metadata
- Ideal for short-term, temporary data rollback
- Effective alongside traditional backup, not a standalone solution
The VM snapshot feature is a valuable tool to safeguard data and maintain business continuity. It’s an agile and reactive option for restoring your operations efficiently without significant resource overheads. While it’s not a standalone feature and shouldn’t be used as a replacement to comprehensive backup, it’s still a worthwhile feature that offers you an additional layer of flexible protection.
Example: For enterprises facing prolonged recovery times and complex backup procedures, utilizing the VM snapshot feature provides rapid recovery and simplified management. You can quickly revert to a previous state, minimize downtime, streamline the data recovery process, and reduce the need for extensive manual intervention. This is particularly useful across complex environments.
Best Practices for VM Snapshots
Regularly Delete Snapshots
Having too many snapshots can degrade system performance by consuming extra disk space. It’s important to regularly delete snapshots once they have fulfilled their intended purpose to maintain optimal system performance.
Implement a Snapshot Alarm
In the case of a VMware VM snapshot, you can set up a snapshot alarm rule to receive notifications when the snapshot size exceeds the appropriate value set. This helps you avoid degradation of system performance. This is accessed via the notification settings.
Use Snapshots Alongside a Comprehensive Backup Strategy
Snapshots are not a replacement for a comprehensive system backup strategy, although they can serve as a temporary backup solution. Relying on them long-term may lead to performance issues if they are kept for extended periods. When choosing a software that includes the snapshot feature, choose a provider who can support your team with the feature, and how it relates to a comprehensive backup strategy.
Want to learn more? Our helpful and comprehensive VM snapshots white paper explores its key features, benefits, and more.
