Introduction

Here on SmallNetBuilder, we've reviewed numerous NAS and storage devices for saving and keeping copies of critical data on your network. Brace yourselves folks, this review is about a new type of data storage technology, one significantly different from a NAS.

CDP, or Continuous Data Protection, is an emerging technology in data storage and backup products that takes the administration and scheduling out of running backups—even enabling end users to restore lost files, as well as providing a solution for offsite disaster recovery—all on a disk-based network appliance.

SonicWALL has a line of CDP appliances for the small-to-medium business, based on the technology acquired through the purchase of Lasso Logic back in 2005. (See the SonicWALL press release). There are four products in the SonicWALL CDP line, ranging from the 1440i to the 4440i. The 1440i is designed to support a network with 15 PCs and three Servers, while the 2440i I'm reviewing can handle up to 30 PCs and five Servers. The higher-level CDP products, the RAID 1 based 3440i and RAID 5 based 4440i, handle greater numbers of PCs and Servers. The 3440i is rated for up to 75 PCs, while the SonicWALL spec sheet simply lists the 4400i as capable of handling more than 75 PCs.

From a technology standpoint, continuous data protection systems manage your data differently than traditional backup systems and software. Traditional backup devices allow for full, incremental, or differential backups. As you know, full backups make complete copies of the designated drives and/or folders. Differential backups make full copies of each file that has changed since the last full backup. Incremental backups make full copies of each file that has changed since the last full or incremental backup.

Continuous Data Protection differs by monitoring when the local machine writes to disk. When write activity occurs in a monitored folder on a PC, the updates are then backed up over the network to the CDP device, creating a continuous update of files.

The continuous data protection solution saves 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. This saves on storage space over traditional incremental and differential backups, which make copies of entire files. In addition, continuous data protection works, uh, continuously, while backup systems run at specific intervals or schedules.

Some files may be updated hundreds of times, and it could get messy if all those changes were saved by the CDP. The CDP will save a maximum of 15 versions of a file, always keeping a copy of the original and latest version, and then a staggered subset of versions to prevent excessive disk utilization.

To summarize, continuous data protection is a more intelligent, efficient, and dynamic backup system, saving only the small amount of data that has changed, and doing so in real time instead of at static intervals.

Tags: NAS, Sonicwall,

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