Cumulative Incremental Backup Volumes

Cumulative Incremental Backup Illustration

Cumulative Incremental (level n)

A Cumulative Incremental (CI) Backup will backup the files that have been modified or created since the most recent lower level backup (level n-1 or lower).

The CI Backup is commonly used by vendors that support multiple backup levels. These multiple level backups are usually defined as level 0 through level 9. A level 0 backup is usually considered a “full” or “complete” backup. Many complex level backup strategies may be implemented. Multiple levels of backup allow site administrators to reduce the frequency of periodic full backups. For simplicity, we will consider a typical 3 level strategy consisting of monthly (level 0), weekly (level 1) and daily (level 2) backups.

The figure above shows how the sizes of two cumulative incremental backup levels, daily (level 2) and weekly (level 1), can change over time. The shape of the curve represents the behavior of a Differential Backup taken over the same time period. Thus, the white space below Days 8 through 13 represents the reduction in the backup size that a three level Cumulative Incremental Backup provides over a Differential Backup strategy. The level 2 daily backup will continue to grow each day as more data is changed on the backup client. Once the level 1 weekly backup completes (Days 7 and 14), the size of the level 2 daily backup is reset and the process starts over. Each week, the size of the level 1 weekly backup will continue to grow until a new level 0 full backup (not shown) is generated. The new full backup will reset the size of the weekly and daily backups and a new backup cycle is started. We use the term cumulative to describe the way this type of backup accumulates data at any given backup level over time.

These graphs were generated using backup statistics gathered from a production backup server. You may have noticed that the Cumulative Incremental backup volume is actually smaller than the sum of the daily True incremental Backup volumes added together. This is because a True incremental Backup volume consists of both new and changed data. The Cumulative Incremental is new or changed data since the most recent lower level backup. Therefore, the CI volume will almost always be smaller than the sum of the TI volumes.

See Also: New Teradactyl white paper on new advancements in synthetic backup consolidation of partial cumulative incremental backups entitled "Partial Cumulative Incremental Backups Offer Unique Advantages to Customers."

NOTE: Alternative Uses of Terminology Explained

Some vendors may refer to the term “cumulative incremental backup” when describing their level 1, Differential Backup, capability. We use the term more generally to describe the behavior of a backup at any incremental level (any level except 0) that accumulates data changes since any previous lower level backup (including level 0). Our ability to generate multiple levels of synthetic backups (not just full or differential) provides our customers with a synthetic backup technology that is far more flexible and advanced.

Some vendors may use the term “differential incremental backup” when describing their True incremental Backup capability. We believe this terminology to be confusing, especially when used in conjunction with the term differential backup, which is also considered a form of incremental backup. Additionally, some vendors may require the use of several available backup levels to implement differential incremental backup. For example, levels 4 through 9 may be needed to configure differential incremental backups on a Monday through Saturday schedule. With only three remaining non-zero backup levels, this may limit the number of ways that other lower level backups can be configured. Our True incremental Backup is implemented as a single Partial Cumulative Incremental (PCI) Backup level and any number of backup levels that may be configured with TiBS.

Three Types of Cumulative Incremental Backup

Direct Cumulative Incremental: A Cumulative Incremental backup that copies Primary Storage on a target system to directly attached Secondary Storage on the target system.

Network Cumulative Incremental: A Cumulative Incremental backup that copies Primary Storage on a target system over a network to Secondary Storage.

Synthetic Cumulative Incremental: A special type of Cumulative Incremental that will consolidate some or all of the Backup Volumes that have been created since the most recent backup at level n-1 or lower on the Backup System. This process is performed by a Backup System with no interaction with the Primary Storage on the target system. The resulting backup volume contains the same data as one that would have been taken from the target system for that period of time.

Additional Backup Volume Resources

Learn About the True incremental Backup System for Enterprise Centralized Network Backup

Three versions of the True incremental Backup System are available. All three versions employ synthetic backup consolidation technology to reduce the load on backup clients and networks. All three versions also have no per seat charges! Learn More ...