Hyper-V 3 virtual machine Snapshot Learning (v) problems found in snapshot applications

For applications deployed in virtual machines, the snapshot Save System State function is the administrator's right-hand man, but the snapshot has the following problems in practice.

1, can not restore the specified file

The specified destination file cannot be recovered. When a critical file or folder in a virtual machine is lost due to misoperation, if you use snapshot recovery, you can only revert to the system state when the snapshot was created, and you cannot restore a specific file as Ntbackup and Windows Server Backup tools, you must restore all of the snapshot content.

2. Takes up too much disk space

The stored snapshot files are new data generated on the virtual machine after the snapshot is written to a separate disk delta file, and the more snapshots you make, the more storage space on the server is occupied. Therefore, administrators are often required to confirm the expiration and unwanted snapshots, and remove them to prevent the lack of storage space, which makes day-to-day management and maintenance more difficult.

3. Increase system load

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When multiple-level snapshots are created, hyper-V needs to check the snapshot tree to find the latest data, requiring the computer to allocate additional resource management snapshots, increasing the load on the computer and reducing system performance.

4, delete the snapshot

In Windows Server 2012, snapshot merges are performed immediately after snapshot deletion, and if the snapshot file is too large, it will take some time for the merge to complete and the virtual machine does not provide external access during the merge. Deleting snapshots is recommended for flying working hours.

5. Snapshots cannot replace backups

Snapshots do not hurt in place of backup reasons:

L A physical server (host) running Hyper-V may fail. For example, a physical server hardware failure or a management operating system failure.

The application running in the virtual machine does not recognize the snapshot and therefore cannot be adjusted accordingly.

L A virtual machine snapshot is different from a backup created by the Volume Shadow Copy Service program.

6, after the snapshot is deleted, but the space is not immediately released

Best solution: Shut down the virtual machine, or force the virtual machine to stop. Deleted virtual machine snapshot files are not removed from physical storage until the virtual machine shuts down, stops, or is placed in a saved state. Deleting a snapshot file may take a while, depending on the size and number of snapshots. In addition, you need to verify that your storage space is adequate.

7. How to store snapshots

A snapshot is a file with a suffix named avhd or AVHDX, and the snapshot file is in the same folder as the virtual hard disk by default. As a result, disk IO performance will determine the performance of snapshot files It is recommended that you deploy snapshot files and virtual machine hard disk files to different physical disks to enhance read and write performance, thereby improving the efficiency of your virtual machine. The snapshot file location can be adjusted with Hyper-V settings.

Author: 51cto Blog Wangshujiang