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+--- Thread: What is a VM checkpoint and how does it work? (/showthread.php?tid=829)
What is a VM checkpoint and how does it work? - savas - 07-02-2023
A VM checkpoint, or snapshot, is like hitting the save button on a video game. Imagine you're playing, and instead of starting all over again after a mistake, you can just go back to a point before things went sideways. That's essentially what a checkpoint does for virtual machines.
When you create a checkpoint for a VM, the hypervisor—think of it as the software that runs your virtual machines—makes a copy of the current state of the VM. This includes the operating system, the applications running, and any data that’s currently in memory. So, if things go wrong later on, you can revert back to that exact moment without having to redo everything from scratch. It’s super handy for testing new software or configuration changes, where you might anticipate some hiccups.
Under the hood, a checkpoint is a bit more complex. When you take a snapshot, the hypervisor doesn’t just make a simple copy of the VM’s files. It creates a separate, read-only disk from that snapshot point, allowing you to continue using the VM without losing any ongoing changes. Any new data written after the snapshot is recorded in a different location, keeping both the old and new information available. This way, when you restore from a checkpoint, the system seamlessly reverts to that saved state while discarding any subsequent changes you made after it.
Another cool feature of checkpoints is that they tend to be fast. Saving the state of a VM is usually quicker than you’d think, thanks to the optimized processes in modern hypervisors. However, taking too many snapshots can lead to performance issues over time, since each new one adds extra overhead. It’s all about balance—keeping enough checkpoints to revert to without cluttering your environment.
But it’s important to note that while checkpoints are great for returning to a previous state, they’re not a replacement for regular backups. Snapshots are more about immediate recovery, while backups are essential for long-term data integrity and safety. If a VM crashes completely or you’re dealing with hardware failures, that’s where traditional backups come into play.
So, in a nutshell, VM checkpoints are a powerful tool in our IT toolbox, giving us that flexibility to experiment and recover without panic mode kicking in. Whether you're a developer testing something new or an admin managing loads of VMs, they’re an essential part of the virtual machine strategy.
I hope my post was useful. Are you new to Hyper-V and do you have a good Hyper-V backup solution? See my other post