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In this type you only backup data files such as important documents, music, pictures, videos and other artifacts that are saved on your computer. Typically, you would exclude files belonging to the operating system, temporary files and installed programs.
In this type you backup the entire disk, regardless of its contents.
| Feature | File level backup | Disk level backup |
|---|---|---|
| Storage space | Less storage is used when you backup individual files. This is because you will omit files belonging to the OS, temporary files and installed programs. This can potentially add up to 5GB on a typical machine. | More space is used. Assume you have 50 employees in a company and on average they have a 500GB hard drive. In order to backup all that data you will need about 25TB disk space on your backup repository. |
| Backup duration | Less time is used to backup data files. Many users do not modify more than 200MB of data on a daily basis and therefore, the amount of time backups take is shorter. Even if 200MB of files change, the actual delta within each file is even smaller, which results in a shorter backup time. | More time is used because entire disk is analyzed to gather blocks that have changed. This typically results in a large delta. |
| Restoration | Files can be easily restored as they are backed up individually. For example, if you mistakenly delete an important document, you can easily retrieve just that document rather than restoring the entire dataset | Restoring a handful of files is not very easy. This would typically involve restoring the entire dataset, restore the desired file and discard the remaining files. |
| Versioning | Versioning individual files are usually a lot easier and older versions can be easily restored. | Versioning will occur at the disk level, resulting in very large deltas. This will not only increase backup durations but will also need a lot of extra disk space. |
| Precise backup sets | Since a user decides what to backup the dataset will most likely contain files that are important to the user. | Some of the files included in such backups are of no use to the user. For example:
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| Viruses/Malware | If a machine is infected with a virus, there is a good chance it won't be attached to the documents. For example, there is no way to attach a virus to a plain text file. Viruses are either self-contained executable programs or they run within another program such as a web browser. | Viruses and Malware programs will also get restored when entire disk is restored. |
| Disk fragments | Not applicable. | Typically, most computers run very fast when you first get them. However, their execution gradually gets slower as data is modified on the disk. One of the major cause of such performance degradation is disk fragmentation. Additionally, most operating systems have a built-in database (such as Registry on Windows) that hold information about other programs. The larger this database, the slower the machine runs. When a disk image is restored, the state of the disk is restored along with fragmented data and large Registry, which will again make the machine run slowly. |
| Crash recovery | Recovering from a crash involves reinstallation of the operating system, reinstallation of all the programs and then finally restoring data files. | Recovering from a crash typically involves restoring just one disk |
| Potential corruption | Most users don't bother checking the integrity of a backed up data until they need to restore it. However, that is often too late. When files are backed up individually, there is a very good chance users will restore one or more files as they use their computer. | The only time someone will usually restore a disk image is when a machine crashes. However, if the backed up data is also bad, you risk losing the entire machine. |