Advantages of Frozen Image Backup; Disadvantages

There is a problem common in backup types such as server-based and client-based backup. With either solution, access to the file is blocked while the file is being backed up. If it just so happens that a user is trying to access that file at the same time that the file is being backed up, that user is out of luck until the backup of that file ends. The backup process locks up the file until it is finished.

This issue may be avoided by scheduling backups outside business hours, so the files won’t be needed during backup. However, some businesses are 24x7. Many companies are global, and their systems are constantly being accessed by someone somewhere on the planet. Other businesses are web-based and require continual access to certain data, such as databases that web users access to make their online financial transactions.

The “frozen image backup” was designed to resolve this type of dilemma, preventing the backup from interfering with file access. Frozen image backup involves taking a “snapshot” of the data, something like a flash photograph that is quickly taken. That snapshot is also referred to as the image of the data. When the backup occurs, it backs up not the actual files but an image of them.

Frozen imaging can be called slightly different terms by different products. In Backup Exec, the Advanced Open File Option provides this ability to take a snapshot of the data source. It is called an “open file” option because it is used to back up files that are open by a program or user during the backup. Normally, open files cannot be archived by a backup program, but the Advanced Open File Option takes a snapshot of all the data and allows a restore that includes files that were open.

Frozen image backups provide significant advantages over other backup types, but there are considerable caveats as well.

Advantages

The frozen image backup has several important advantages:

• It allows the backup to take place without interfering with data access.

• The technique also results in faster backups and restores.

Disadvantages

The disadvantages of the frozen image backup include the following:

• Software for creating a frozen image may not be included in the backup software. You may need to purchase this software separately as an option to your backup program or as an additional, third-party tool.

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  I/O (input/output) demands increase. During the frozen image backup, there will be a peak of resource usage in the network, hard drives, computer CPUs, and any other hardware involved.

• The storage demands for a frozen image are higher than for a regular backup. You will need to have enough space for your frozen images and your archived data as well, as these two are separate.

• With a frozen image, you can’t just restore one file from your backup as you can with other kinds of backup. You need to restore the whole image. This makes individual file restoration impossible, unless you want to restore everything just to recover one file.

Frozen imaging is an important technique to use, since it allows faster restores of large amounts of data. It is useful for disaster recovery to replace entire systems that go down. However, because it can only restore large amounts of data and not small ones if needed, it can only serve as a complementary backup technique for the more traditional backup.