Hyper-V Virtual Machine Snapshot technology

The snapshot function provided by Hyper-V Manager records the status of the virtual machine operating system at a certain time point. After completing system updates, the administrator can use a snapshot to restore the VM to the status before the update. The administrator can create multiple snapshots for the Virtual Machine and restore them to any point in time when the snapshots are taken. Snapshots are only saved on virtual machines and cannot be used as regular backup methods.

1,Snapshot Overview: Snapshots can record the complete status of the virtual machine at a certain time point. The VSS technology captures the current system status, and all the statuses of the virtual machine at a certain time point can include memory, disk, network, and files) capture an image file. At any time in the future, you can use a snapshot to restore the current time status.

2,Snapshot use cases:System-level test patch updates, software Bug fixes), and new business systems are more capable of testing.

3,Snapshot Creation Time:Administrators can create snapshots at any time. After a snapshot is created, it is automatically embedded in the snapshot tree of the virtual machine. You can view the snapshot details in the snapshot properties. :

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4,Data Processed by snapshots:After the Administrator creates a snapshot, data cannot be written to the original virtual disk. After the snapshot is captured, all disk updates are written to the snapshot file suffixed with "avhd" or "avhdx. At the same time, the VM memory will be backed up during snapshot capturing, that is, two tasks will be executed during snapshot creation: copying one copy of the VM memory at that time, occupying less disk space; create a snapshot file with the suffix "avhd" or "avhdx" for differential backup, after that, all data that should be written to the disk will be written to the snapshot file with the suffix "avhd" or "avhdx", keeping the original vhd or vhdx files unchanged. For the snapshot file and the snapshot structure after the snapshot is created:

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5,Problems found in the Snapshot Application:After deploying a virtual machine, snapshots are a very useful tool in Hyper-V management. However, in actual applications, snapshots have the following problems.

5.1: The specified file cannot be restored:Due to misoperations, when an important file or folder in the virtual machine is lost, if the snapshot is used for restoration, it can only be restored to the system status when the snapshot is created, files cannot be restored like the tools "WindowsServerBackup" and "Ntbackup.

5.2: Occupying too much disk space:After a snapshot is taken, the new data generated by the VM is written to an independent incremental disk file. The more snapshots, the more disk space occupied. Therefore, if too many snapshots are created, the administrator needs to regularly confirm that the snapshots have expired and are no longer needed, and delete them.

5.3: Increase system load:After creating a multi-layer snapshot, Hyper-V needs to check the snapshot tree to find the latest data. The computer needs to allocate more resources to manage snapshots. This will increase or decrease Computer load and reduce system performance.

5.4: Snapshot cannot replace backup solution:The Hyper-V host may fail, and the running virtual machines and Virtual Machine snapshots cannot be used. The applications running in the virtual machine cannot identify snapshots.

This article is from the Eric1990 blog, please be sure to keep this source http://eric1990.blog.51cto.com/2298455/1298963