SnapShot is a technology for creating snapshots that allows you to take snapshots of data (file system, virtual machine) for the possibility of returning them to a working state in case of a failure.

The essence of the technology

At the moment of the snapshot creation, writing to the disk drive stops, which allows you to take a snapshot of the disk, and perform all further operations in a separate file.

In order to get data from the disk in the future, you first need to read the contents of the snapshot, then link and take into account all disk operations that were performed after the snapshot was created and recorded in a separate file.

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If it becomes necessary to return the virtual machine or file to its original state, then you only need to delete the files with the changes, continuing to use the disk from the moment when the snapshot was taken.

Snapshots of file systems and virtual machines

A virtual machine is a data file that includes the contents of a virtual hard disk, RAM, processor registers, and a description of the configuration of the virtual machine in a language understandable to the hypervisor.

Therefore, you can do everything with a virtual machine that you do with file systems, including creating copies of them-snapshots. As soon as such a copy is created, it will be written to the hard disk.

And all subsequent changes in the virtual machine or file system will be written to another file, and all further work will be reduced to changing this particular file.

If you create another snapshot after a while, a new file will be created, in which all changes will remain recorded. And there is always an opportunity to go back to a specific snapshot.


The technology of creating snapshots has the following features:

  • snapshots are saved near the virtual disks on the basis of which they are created;
  • the number of snapshots is constantly growing, and their size may exceed the size of the file system itself or the virtual machine;
  • snapshot files are backed up dynamically, which has a bad effect on machine performance;
  • the “lifetime” of each snapshot should not exceed 72 hours, otherwise the operation of the virtual machine will slow down significantly.

And even though many people call SnapShot one of the types of backup, snapshots of file systems cannot be called a full-fledged backup, since they contain only file change histories.

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