There are three basic types of backups: full, incremental and differential. More recently though, some new types of backup were introduced, which offer some advantages over the three classic forms. Before we get into the Backup method used by XXL Cloud we will explain how the classic methods work.
A full backup is exactly what the name implies. It is a full copy of the entire data set which needs to be kept for archival purposes. Although full backups offer the best protection, most organizations only use them on a periodic basis, simply because they are extremely time consuming, and often require a large amount of storage space which needs to be permanent and dedicated to the historical backup copies being kept.
Because full backups are extremely time consuming, incremental backups were introduced as a way of decreasing the amount of time required to do a backup. Incremental backups only backup the files that have changed since the previous backup copy.
A differential backup is almost like an incremental backup, the difference is that it starts with a full backup, and subsequent backups only contain files which have been changed.
The difference is that while an incremental backup only includes the data that has changed since the previous backup, a differential backup contains all of the files that have changed since the last full backup.
XXL Cloud uses one of the newer backup methodologies referred to as "incremental-forever".
Incremental-forever backups are often used by disk-to-cloud-to-disk backup systems like XXL Box. The basic idea is that like an incremental backup, and incremental-forever backup begins by taking a full backup of the files. After that point, only incremental backups are taken.
The forever stands for a continuous process in which files added or changed in the range of synchronized libraries are taken and added, or modified within the backup copy which resides in the storage cloud.
What makes the incremental-forever backup different is that all data is continuously available, just like your hot data you keep on your hard drives.
Files which are changed are stored as revisions of the original copy and remain available in the form of snapshots. Revisions are kept for as long as required, normally 30 days, but this setting is flexible and can be changed as required.
There is no limitation to the amount of files or folders which can be included in a Backup. You are only limited by the overall available storage space within your XXL Box Account.