This article gives a short introduction to Continuous Data Prodection (CDP) and has some links for further reading. CDP is a relatively new and promising backup technology.
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This article is the first of a series about Continuous Data Protection (CDP), I intend to write. In my view, the future of all backup systems belongs to CDP. In this introduction, I will try to explain the concept of CDP. A review of some popular CDP solutions will come later.

I can only try defining CDP, because there is no clear-cut use of the term. CDP has only become a buzzword recently, and vendors of replication tools, backup software, and snapshot tools apply this term to different kind technologies.

What all CDP systems have in common is that their client intercepts the write process of server applications to the hard disk. This way they log all changes to continuously secure the data. However, "continuous" can have two different meanings in the context of replication and backup tools. It can mean that only the copy process itself is running continuously or that one can restore the data to an arbitrary point in time.

Often replication tools only support continuous data protection in the first sense. They just store one copy of the data to be secured. The main purpose of replication tools are fail-over scenarios where the whole server has to be replaced by a backup server. Real CDP backup tools on the other hand allow point-in-time restoration which means that not only the backup process, but also the possible recovery points are "continuous" in some sense. They are often used to restore the state of a file to a certain point in time in the past.

The problem with this distinction is that there are some tools which fall in between those two categories. They store different copies of the data, but one can't restore to any point in time. Usually there is one hour time difference between two restoration points which is better than with traditional backup tools though. Conventional backup software only runs once a day during non peak periods, the so called backup window. This means that in worst case, you lose data changes for one day. So in some sense these kind of new backup solutions are continuous since they reduce the RPO (Recovery Point Objective).

Microsoft coined the term "near continuous data protection" for its Data Protection Manager (DPM). Another exponent of this kind of backup software is Symantec's Continuous Protection Server (CPS) which is now bundled with Backup Exec. Real CDP systems need expensive hardware since the required processing power to calculate the snapshot from the change logs can be enormous. Well known vendors of CDP Systems are Revivio and Medocino. Near CDP systems like Microsoft DPM or Symantec CPS run on typical server hardware.

I only summarized the basic concepts and distinctions about Continuous Data Protection. If you want to learn more about this topic, I recommend the following articles:

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  1. Greg Muir 17 years ago

    Pulling my hair out with backup exec. I hear that the new 11d version sucks even harder than 10d. Any alternative solutions to recommend?

  2. Steve 17 years ago

    You heard wrong. I’ve been using it since release and it works flawlessly. Minor issues here and there, but nothing to scream at, and EVERY software application, upon release, has ‘issues’ to speak of. Granular restore capability is awesome. Stability is great. Alternative solutions? Sure. NTBackup.

  3. Greg Muir 17 years ago

    There are others posting here who would disagree with you.

  4. Actually, I would disagree, too. It works, but I wouldn’t say that it works flawlessly. Since Veritas bought Backup Exec, it never really worked without any problems. I think, it even got worse when Symantec bought Veritas. I still remember the times when Backup Exec was owned by Seagate. At that time, it was really a great backup tool.

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