Shulou(Shulou.com)06/03 Report--

What is a virtual machine snapshot? In view of this problem, this article introduces the corresponding analysis and answers in detail, hoping to help more partners who want to solve this problem to find a more simple and feasible way.

A virtual machine snapshot is a mirror with a read-only attribute for a specific file system at a specific time, which means that when a user needs to return to a certain system state repeatedly and does not want to create multiple virtual machines, you can use the virtual machine snapshot feature.

Principle of virtual machine

The essence of taking a snapshot of a virtual machine is to record the disk data of the virtual machine at a certain point in time. Take KVM as an example, the disk of the virtual machine in KVM uses the image file of qCow2 format, and the virtual machine has several qCow2 files if it has several disks. Therefore, recording the disk data of the virtual machine at a certain point in time is a snapshot of the qCow2 image file. The data generated by the virtual machine snapshot is stored in the same qCow2 image file as the virtual machine disk data, so the storage location is the storage location of the virtual machine itself, that is, if the storage where the virtual machine is located cannot be accessed, the snapshot cannot be restored. QCow2 snapshot adopts the technology of "copy on write (Copy On Write)", and the implementation principle is relatively simple. When taking a snapshot, copy an index of the original disk, and the actual data pointed to are the data of the original disk. Only when the data of the original mirror changes, will the data before the change be copied to the corresponding location of the snapshot. So when you take a snapshot, the data is relatively small, and then it will get bigger and bigger.

This is the answer to the question about what the virtual machine snapshot is. I hope the above content can be of some help to you. If you still have a lot of doubts to be solved, you can follow the industry information channel to learn more about it.

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