What are Snapshots


Digitized information is very easy to lose. This simple rule is known not only by developers but also by ordinary users. That is why the task of preserving digital data is extremely urgent for any owner of computer equipment. This can be done using a backup. This feature allows you to create copies of both individual files on the computer and server, as well as their entirety. Moreover, today it is possible to copy even disk volumes or operating systems.

Pros and cons of backup

The main advantage of backup is the ability to quickly restore any data. But a backup (this is what it is customary to call a backup copy of digital data) does not always allow you to completely restore the operation of a disk or OS. This problem is most often due to the fact that immediately after the backup, a significant change in the copied data may occur. Consequently, many files and applications of the OS change and can no longer be associated with the copy.

Therefore, before making a backup, you should use a snapshot. This term refers to a snapshot or photograph. Snapshot allows you to "roll back" the OS to the point at which the snapshot was taken.

Snapshots are used when you want to return to the same state of virtual machines without the need to create new ones.

Snapshots contain the following information:

  • Virtual machine settings;
  • The state of the virtual machine disks;
  • Contents of virtual machine memory.

Snapshots - what they are and how to use them

The first thing to say is that a snapshot of a virtual machine can be executed even on a powered-off device. It should also be noted that taking a snapshot pauses the computer for a few seconds. But then the machine continues to work in its previous mode.

Snapshot can be taken in two ways:

  • on the disks page;
  • on the page with virtual machines (the "roll back to the previous snapshot" button).

All created snapshots of the file system can be found on the page with disks. The peculiarity of "snapshots" is their size. Snapshots weigh an order of magnitude less than disks. Another feature is that the pictures taken are a kind of chain or tree. Therefore, if you delete one of the images, its "neighbors" will merge with each other. The process of deleting unwanted images does not take long.

This is how snapshot trees look like on Windows and Linux:

A significant advantage of snapshots is their large number. Developers can take up to 60 pictures, thereby insuring themselves against accidental loss of important information. But do not overdo it, after all, snapshots also "load" RAM, and therefore there is a possibility of certain limitations in the functioning of the virtual infrastructure. Therefore, any developer should be aware that long-term storage of the snapshot is not advisable.

Save money and time when using a snapshot

Having figured out what a snapshot is and how it works, you can go on to describe the main advantage of this feature - saving money and time. The financial benefit stems from the fact that sometimes lost digital data can cost a lot of money. At the same time, storing snapshots of disks or OS on virtual servers costs several rubles per 1 gigabyte of information.

As for saving time, the snapshot function allows you to restore all files and normal operation of the disk (OS) within a few minutes. Thanks to the snapshot, developers can be insured against financial and time losses.

Differences between Backup and Snapshot

Some users often confuse a snapshot with a backup (backup). But these two functions have completely different mechanisms of action.
Backup provides for the archiving of a specific part of the system (or the entire system as a whole). Backup is a lengthy process that forces you to stop all disk operations on the part of the file system that is to be copied. The main problem with backup is the ability to change the copied areas. In the backup, these areas remain unchanged. That is why problems often arise with the restoration of the operation of various services.

Snapshots do not require stopping operations and are carried out within a few seconds. Thanks to this, services do not have time to change and, therefore, can be restored without problems if necessary.

Advantages of fast rollback of changes when using snapshots

Snapshot technology has the following advantages:

  • automation of the archiving process;
  • no impact on overall file system performance;
  • the ability to use the maximum disk capacity at the minimum cost of the service;
  • data security;
  • scalability.

Separately, it should be said about the security of the copied data. The virtual machine snapshot protects information from writing and provides it in ReadOnly mode. Therefore, the snapshot stores only undamaged and static copies that can be restored in case of accidental damage or deletion of the original data.