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Continuous data protection: Pros and cons for SMBs

Until recently, SMBs were less likely to implement continuous data protection (CDP) due to its cost and complexity. In the first part of our series on CDP, we'll examine when to consider CDP and deploy it in the SMB space.

Until recently, SMBs that were running only one server and a handful of laptops were less likely to implement continuous data protection (CDP) due to cost and complexity. But vendors are now capitalizing on Storage as a Service (SaaS) and the continued acceptance of disk-to-disk data backup to expand their CDP offerings and bring data center protection to SMBs. In the first part of our series on CDP, we'll examine the pros and cons of CDP and where to deploy it.

Understanding the benefits of CDP

The motivation for implementing CDP is to protect data from loss, corruption or unauthorized alteration in a manner that is more granular than the daily backup. This need to protect and recover data incrementally is realized by the ability to go back in time and reset a file, dataset or entire database to the state it was in before an incident occurred, such as a manual deletion or accidental corruption.
Given this ability to resolve data issues, the benefits of CDP include:

  • Improved recovery point objective (RPO) and recovery time objective (RTO) service levels
  • Self-service for desktop and laptop users. Like many other self-service enabling technologies, this allows the storage staff to stay focused on the higher order operational matters
  • Integration with current backup applications. CDP applications that provide the monitoring and management hooks into established data protection frameworks are easier to integrate and manage as well as protect the data on other storage tiers

How CDP works

CDP systems may be block-, file- or application-based and can provide fine granularities of restorable objects to infinitely variable recovery points. In simpler terms, continuous data protection includes these basic functions:

  • A baseline reference to the original state of the data -- an original backup that all future changes to the data are based on
  • Continuous or near-continuous tracking of the state of a file, block or volume to recognize when a change has occurred and record the change to the backup system
  • Granular recovery for multiple point-in-time states of the data

CDP works by incrementally backing up the changes in the state of the data over some period of time or when a record, file or block of information is created or updated. In some cases, there is only one initial full backup and all subsequent backups are incremental to the original backup. This "incremental forever" approach is in contrast to the standard techniques for data backup, but has been gaining greater adoption.

When to consider continuous data protection

The need for CDP is most often established in order to meet a formal service-level agreement (SLA) with a business unit, or often through an informal commitment to deliver a specific level of data protection. A business unit or application may indicate that a specific application cannot lose more than a minute or two of data, and must be able to be restored to operation within a few minutes. In such cases, traditional backup and recovery tools cannot deliver the RTO and RPO levels required. Thus, CDP is one of the best options to deliver the required service levels cost effectively.

Where to deploy CDP

For SMBs looking to provide data protection for business-critical files to users who depend on the availability of their data, CDP can make a significant difference. CDP not only reduces the impact of mistakes or accidents, but also provides the ability to restore data after the loss or theft of a laptop.

Both enterprise and SMB environments may benefit from CDP because of the significant improvement over the traditional daily backup process. However, SMB and small office/home office (SOHO) environments may see the largest benefits due to the lack of data protection processes and procedures in place within many of these environments.

How CDP is deployed

In order to deploy CDP, a location is required to store the changed data. In the case of enterprise CDP applications, data is often stored on the local storage area network (SAN) or network-attached storage (NAS) system. Typically the data is also replicated to one or more locations for disaster recovery (DR) purposes.

In contrast, CDP products designed for SMB environments often utilize local storage on the system being protected, as well as a remote storage location for DR purposes. Many of the SMB CDP products utilize an internet-connected repository for storing data, which provides storage as a service type of model.

The downsides of CDP

A primary concern is that CDP, backup, replication and snapshot technologies often function independently. Storage administrators and end users alike are looking to protect data, with minimal impact to operations. However, the trend is clearly towards tighter integration, which will address many of the integration issues.

What this means is that users will be better able to protect data from a high-level policy perspective. The protection policy is established by the user in the backup application, and then the application uses technology (like CDP) to help implement the policy. CDP is really just a technology tool and is not a solution in and of itself.

Another potential issue is how system performance (CPU, network throughput, etc.) may be adversely impacted by the protection process, especially when there are limited windows of opportunity to replicate data to corporate storage systems.

In some cases, the term "continuous" can be a bit misleading because CDP applications have varying degrees of granularity. For desktop/laptop applications, the granularity is typically tied to the last time the file was created or a new version was saved. This is why some products describe their capabilities using the term "near continuous." For enterprise applications, the granularity is usually based on a configured time interval, using periodic snapshots to determine what can be restored.

In the next part of our series on CDP for SMBs, we'll look at CDP product offerings.

About the author: Russ Fellows is a Senior Analyst with Evaluator Group. He is responsible for leading research and analysis of product and market trends for NAS, virtual tape libraries and storage security.

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