How do snapshot backups work

These copies are traditionally kept in a different location than the original content, thus making them ideal for disaster recovery. Our ShadowDrives and File Backups are all stored off server. However, some backups, such as website and database dumps, remain on server.

Backups are a process that could take minutes, hours, or days to complete, depending on the data. This means that the data at the end of the backup may not be consistent with the data at the time when the backup started. Backups are designed to be stored for long periods of time and, if they are stored off server, they can be used to restore servers after server failure. Snapshots are an instantaneous "picture" of your server's file system at a certain period of time.

Because your snapshot has the metadata, it can recognize what blocks of data have been added or changed since the creation of the snapshot. If you revert to one of your snapshots, every block of data that was added or changed since the snapshot was taken is removed from where it is saved in the snapshot. Then every block of data is as it was at the time the snapshot was taken. And since your files are made up of blocks of data, every file is now as it was when the snapshot was taken. This allows you to undo changes to your files, folders, and even volume, or to bring back files you have deleted accidentally.

Just click on what snapshot you want to load, and then you can revert the whole volume or select a specific file or folder to restore. Because QNAP does block level snapshots, they are more space efficient than file level snapshots. With file level snapshots, if you make even a small change to a file, you need to save the whole file to the snapshot. But with block level snapshots, you only need to save the blocks within the file that have been changed. QNAP built their snapshots from the ground up and gave you more control of how space for the snapshots is allocated.

You control how much storage to reserve for the snapshots. And other files and applications will have priority over the space that you did not allocate to snapshots. The Snapshot just needs to have the metadata recording what blocks have been added to the NAS since the creation of the snapshot. When you delete files, the snapshot needs to be able to restore the files you deleted.

To do that, any block of data you delete and overwrite will be saved to the snapshot. Saving blocks of data to the snapshot takes much more space than just saving metadata. So, deleting files makes your snapshot size grow much more than adding file. Some may argue that this is not a snapshot but in fact it is, as it records the state of the drive s at a point in time. The technology used will be dependent on the running system. Windows Volume Shadow Copy is a form of snapshot technology.

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It is used in backup processes to restore the system or disk of a particular device at a specific time. It is not equivalent to a backup copy and it doesn't store the data itself but just defines where and how the data was stored and organized. However, most backup software can also take snapshot backups and restore the system using the snapshots.