Continuous data protection
Encyclopedia
Continuous data protection (CDP), also called continuous backup or real-time backup, refers to backup of computer
data
by automatically saving a copy of every change made to that data, essentially capturing every version of the data that the user saves. It allows the user or administrator to restore data to any point in time.
CDP is a service that captures changes to data to a separate storage location. There are multiple methods for capturing the continuous changes involving different technologies that serve different needs. CDP-based solutions can provide fine granularities of restorable objects ranging from crash-consistent images to logical objects such as files, mail boxes, messages, and database files and logs.
s, an example of which is CDP Server
, disk-based backup software that periodically creates restore points using a snapshot and volume filter device driver to track disk changes. There is some debate in the industry as to whether the granularity of backup needs to be "every write" in order to be considered CDP or whether a solution which captures the data every few seconds is good enough. The latter is sometimes called near continuous backup. The debate hinges on the use of the term continuous: whether only the backup process needs to be continuous, which is sufficient to achieve the benefits cited above, or whether the ability to restore from the backup also has to be continuous. The Storage Networking Industry Association
(SNIA) uses the "every write" definition.
, or mirroring
in that these technologies only protect one—the most recent—copy of the data. If data becomes corrupted in a way that is not immediately detected, these technologies will simply protect the corrupted data.
Continuous data protection will protect against some effects of data corruption by allowing to restore a previous, uncorrupted version of the data. Transactions that took place between the corrupting event and the restoration will be lost, however. They could be recovered through other means, such as journaling.
Computer
A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...
data
Data
The term data refers to qualitative or quantitative attributes of a variable or set of variables. Data are typically the results of measurements and can be the basis of graphs, images, or observations of a set of variables. Data are often viewed as the lowest level of abstraction from which...
by automatically saving a copy of every change made to that data, essentially capturing every version of the data that the user saves. It allows the user or administrator to restore data to any point in time.
CDP is a service that captures changes to data to a separate storage location. There are multiple methods for capturing the continuous changes involving different technologies that serve different needs. CDP-based solutions can provide fine granularities of restorable objects ranging from crash-consistent images to logical objects such as files, mail boxes, messages, and database files and logs.
Differences from traditional backup
Continuous data protection is different from traditional backup in that you don't have to specify the point in time to which you would like to recover until you are ready to perform a restore. Traditional backups can only restore data to the point at which the backup was taken. With continuous data protection, there are no backup schedules. When data is written to disk, it is also asynchronously written to a second location, usually another computer over the network. This introduces some overhead to disk-write operations but eliminates the need for scheduled backups.Continuous vs near continuous
Some solutions which are marketed as continuous data protection may only allow restores at fixed intervals such as 1 hour, or 24 hours. Such schemes are not universally recognized as true continuous data protection, as they do not provide the ability to restore to any point in time. Such solutions are often based on periodical snapshotSnapshot (computer storage)
In computer systems, a snapshot is the state of a system at a particular point in time. The term was coined as an analogy to that in photography. It can refer to an actual copy of the state of a system or to a capability provided by certain systems....
s, an example of which is CDP Server
CDP Server
R1Soft Continuous Data Protection is a near continuous backup application for Windows and Linux computers, developed by R1Soft. The software provides user scheduled near continuous disk-based online backups for one or more Windows or Linux servers...
, disk-based backup software that periodically creates restore points using a snapshot and volume filter device driver to track disk changes. There is some debate in the industry as to whether the granularity of backup needs to be "every write" in order to be considered CDP or whether a solution which captures the data every few seconds is good enough. The latter is sometimes called near continuous backup. The debate hinges on the use of the term continuous: whether only the backup process needs to be continuous, which is sufficient to achieve the benefits cited above, or whether the ability to restore from the backup also has to be continuous. The Storage Networking Industry Association
Storage Networking Industry Association
An association of producers and consumers of storage networking products, whose goal is to further storage networking technology and applications.The Storage Networking Industry Association, or SNIA, was incorporated in December, 1997, and is a registered 501 non-profit trade association...
(SNIA) uses the "every write" definition.
Differences from RAID/replication/mirroring
Continuous data protection differs from RAID, replicationReplication (computer science)
Replication is the process of sharing information so as to ensure consistency between redundant resources, such as software or hardware components, to improve reliability, fault-tolerance, or accessibility. It could be data replication if the same data is stored on multiple storage devices, or...
, or mirroring
Disk mirroring
In data storage, disk mirroring or RAID1 is the replication of logical disk volumes onto separate physical hard disks in real time to ensure continuous availability...
in that these technologies only protect one—the most recent—copy of the data. If data becomes corrupted in a way that is not immediately detected, these technologies will simply protect the corrupted data.
Continuous data protection will protect against some effects of data corruption by allowing to restore a previous, uncorrupted version of the data. Transactions that took place between the corrupting event and the restoration will be lost, however. They could be recovered through other means, such as journaling.
Backup disk size
In some situations, continuous data protection will require less space on backup media (usually disk) than traditional backup. Most continuous data protection solutions save byte or block-level differences rather than file-level differences. This means that if you change one byte of a 100 GB file, only the changed byte or block is backed up. Traditional incremental and differential backups make copies of entire files.Risks and disadvantages
The protection afforded by continuous data protection is often heralded without consideration of the disadvantages and challenges that it can present. Specifically, the continuous bandwidth usage can adversely affect network performance, especially in operations where file sizes are large, such as multimedia and CAD design environments. To mitigate this risk, companies employ throttling techniques which prioritize network traffic in order to reduce the impact of backup on day-to-day operation.See also
- BackupBackupIn information technology, a backup or the process of backing up is making copies of data which may be used to restore the original after a data loss event. The verb form is back up in two words, whereas the noun is backup....
- Disaster recoveryDisaster recoveryDisaster recovery is the process, policies and procedures related to preparing for recovery or continuation of technology infrastructure critical to an organization after a natural or human-induced disaster. Disaster recovery is a subset of business continuity...
- Single instance storage
- List of backup software
- List of online backup services
- InMage DR-ScoutInMage DR-ScoutInMage Scout is a Continuous Data Protection based backup and replication solution. Scout consists of two product lines: the host-offload line, which uses a software agent on the protected servers, and the fabric line, which uses an agent on the Fibre Channel switch fabric. The software protects...
- R1Soft Continuous Data Protection
- EMC RecoverPointRecoverPointRecoverPoint is a continuous data protection solution offered by EMC Corporation which supports asynchronous and synchronous data replication of block-based storage.- Capabilities :* Block-based journaling....
- Cofio SoftwareCofio SoftwareCofio Software, headquartered in San Diego, California, is a privately held company founded in 2006 by Tony Cerqueira, Patrick Barcus and Fabrice Helliker. The founders were also founders of BakBone Software and much of Cofio's engineering team were the core developers at BakBone and were the team...
External links
- near-Continuous vs. True CDP
- Categories of Backup Software
- CDP is a Dog - Unless its Unified with Backup
- Continuous Data Protection for programmers An article on how CDP can help programmers.