Hyper-V 3 virtual machine Snapshot Learning (i) Introduction to snapshot applications

What is a snapshot

Snapshots can record the full state of a point-in-time virtual machine operating system and crawl the current system state through the Microsoft Volume Shadow Copy Service (Volume Shadow Copy Services) technology, and you can put all the states of a virtual machine at some point (memory, disk, network, files, etc.) crawled as a mirrored file, and at any later time, the actual state could be restored by snapshot. As with the camera feature, the state of a point in time is fixed.

Under what circumstances is a snapshot used

In Hyper-V, snapshots are easy to use, available at all times, and easy to create and apply. Snapshots are like a digital camera, the technology behind the scenes is complex, but the operation is simple and easy to understand. Under what circumstances does a snapshot need to be used?

L system-level testing, including patch updates, bug fixes, etc.

L Business System new function test.

In the above application, it is recommended that you first create a snapshot and then test the system. Note, however, that snapshots are not equivalent to backups and cannot be used as a method of regular backups.

What time can I create a snapshot

Snapshots can be created for the virtual machine at any time and automatically embedded in the snapshot tree of the virtual machine when the snapshot is created. In the snapshot properties, you can view the details of the snapshot. The virtual machine settings in the snapshot are read-only. A snapshot tree example is shown in Figure 1.

Figure 1

Data to be processed by the snapshot

After the snapshot is created, the original virtual disk file (VHD or VHDX) cannot write data. After capturing the snapshot, all disk updates are written to another snapshot file with the suffix "avhd or AVHDX." It also backs up the memory of the virtual machine while it is crawling. That is, when the snapshot is crawled, two tasks are done simultaneously (each grab snapshot completes two tasks):

First, copying a copy of the virtual machine memory at that time, taking up less disk space.

Second, create a new snapshot file with a suffix of "avhd or AVHDX" for differential backups, after which all data that should be written to the disk will be written to the AVHD or AVHDX file, keeping the original VHD or VHDX file unchanged.

The snapshot files created by the virtual hard disk in VHDX format are shown in Figure 2.

Figure 2

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