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Replicating data every 15 minutes
Alexander Dubose Jones and Townsend LLP, a small appellate law firm with offices in Houston and Austin, Texas, moved from tape to LiveVault Corp.'s InSync (LiveVault service), a continuous data protection product. Vicki McArthur, the firm's administrator (above), says they had previously relied on daily tape backup as well as on a seven-day offsite tape rotation. The firm experienced all of the challenges traditionally found in tape environments, but recoveries concerned McArthur the most. Nightly backups don't work well with

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the nature of the legal industry, where files often require last-minute changes. Under a traditional backup system, files created in the morning wouldn't get backed up until that night, and wouldn't be sent offsite until at least the next day. "We faced the possibility of losing an entire day's worth of work or worse," says McArthur.

LiveVault makes a backup of files as soon as they're saved, and then replicates them to a remote site within a few minutes, where all previous versions of any file are accessible at any time. Because only changed bytes are sent, very little bandwidth is required. And since data is replicated every 15 minutes, McArthur believes that "the amount of data loss due to user error is reduced to minutes, possibly less."

Aggressive requirements
You should only consider switching backup products if your current backup product can't meet your requirements (see Pros and cons of alternative backup methods). There are a number of requirements that might prompt you to consider alternatives, such as:

  • Remote office data protection
  • Backing up large databases
  • An application with an RPO of zero

The most common area where backup requirements are difficult to meet is the remote office. Traditional backup schemes can't meet remote office RTO/RPO requirements. There's either too much data or not enough bandwidth to support a reasonable RTO or backup window. Any CDP product can provide backup and recovery of a remote office; most offer two methods. If long RTOs are acceptable, remote sites can back up directly to your central office. In the case of a disaster, just copy the data from the central data center to a disk or tape and send it to the remote site. If this meets RTO requirements, it's the least-expensive option. For tighter RTO requirements, install a backup device at the remote office. The remote office systems can back up to it, and it can then replicate the data to the central site. This provides local recovery and disaster recovery without touching a tape.

CDP products are also superior to traditional backup methods when backing up very large databases. There isn't enough time or horsepower available to transfer several terabytes of data to tape every day. A CDP product could continually back up a database throughout the day, with no noticeable backup window or application impact. Depending on the product, a stringent RTO and short RPO could also be met. Also, some products provide a disk-based copy that can be used in a disaster situation while the real volume is being recovered.

Finally, some database applications require a zero RPO. Most databases can meet such a requirement if they're configured correctly, and if the transaction log is backed up throughout the day. If your database supports that kind of functionality, it's probably best to stick with it. If not, try one of these newer methods.

This was first published in June 2005

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