Set up a green disk to disk backup

During the recent period, two of the many priorities that storage managers face seem to be mutually exclusive: disk to disk (D2D) backups seem to contradict the energy savings.

Storage experts deploy disk to disk Backup in 2008, or expand their investment in this area to improve data protection performance and secure data recovery. Compared to traditional tape-based data protection, disk to disk has proven to shorten backup windows, improve recovery speed, and improve the reliability of some cumbersome backup processes.

At the same time, storage experts are facing a crisis in the use of electricity. This is not only because of green concerns, but also because of the growing demand for electricity. A chief technology officer recently told me: "I don't care if it's green." I just can't get enough power to support my data center.

Unfortunately, despite all the drawbacks, tape is better than a disk solution in this area, and it's very energy efficient. Let's see: a tape that fills a cardboard box will not consume much electricity. Even if these tapes consume related resources and have a certain environmental impact because of the need for some storage supplies, the need for trucks to carry them, and the associated temperature control facilities, tapes are still less energy-efficient than D2D solutions.

The question is: can we add or expand disk to disk backup without having to face power problems?

Fortunately, the answer is probably "yes". Let's look at the problem more closely and systematically summarize the techniques used by D2D and the ways in which they can improve their energy efficiency.

Basic considerations

Before we get to the center of the problem, we need to review two basic principles: first, more efficient use of space (storing more data in smaller spaces). It is the most practical solution to the problem of energy efficiency. Second, becoming greener requires more technology that improves energy efficiency.

In fact, in 2008, the path to server virtualization and storage virtualization represented the way to store data with less physical space and less energy. On storage, duplicate data deletion is another technology that can make more efficient use of electricity. Fewer physical servers or physical storage means less energy requirements.

But technologies such as virtualization and duplicate data deletion do not exist out of thin air. To effectively improve disk to disk energy efficiency, you need to check the energy consumption of each product category and how to improve its efficiency.

The various comparison data used below are based on the public energy consumption specifications of each vendor. Although the deployment of each data center is unique, in terms of percentages, the differences between the different technologies are similar.

D2D Product Type: Virtual Tape library (VTL)

Power consumption: Consumes about 80 watts per usable TB

Explanation: Virtual tape libraries do not directly produce green effects. If the virtual tape library is properly deployed, it may be a catalyst for other energy-saving scenarios-such as maid (large inactive disk arrays) or de-duplication-but now the traditional virtual tape library is just a stack of front-end racks of not-optimized SATA disk racks. These disk racks are large energy-consuming and heat-producing large data centers.

If you decide to connect to the disaster recovery site over a WAN and replicate your backup to the disk, the situation is even worse. Because Virtual tape library solutions lack space efficiency, you must repeatedly invest in the same capacity at the disaster recovery site. Of course, the result is double power, cooling and cost. On average, most standard virtual tape library solutions consume about 80 watts of power per usable TB capacity. In addition, because there is no capacity optimization, the entire backup must be repeated, so the disaster recovery site must be connected through a very high-bandwidth network, and the site cannot be too far away.

The first step in optimizing a traditional virtual tape library is to compress the data on the disk, similar to compressing the data on the tape. While this can reduce power consumption to 50 watts per usable TB, doing so also poses a problem.

First, most virtual tape library solutions lose more than 60% of their performance when using compression, and the ability to receive data in the backup process can be severely compromised. This runs counter to one of the primary purposes of adding disks to the backup process-shortening the backup window.

Compression on the disk also complicates the tape situation. If you use tape--you do it in the case of most virtual tape library solutions--it's not always possible to transfer data that has been compressed to tape and compress it with a tape drive. You will need to turn off tape compression on the tape drive.

Another possible solution is to make the portion of the disk in the virtual tape library smaller and to speed up backup from disk to tape. With this strategy, you rely on tape for data recovery just as you did when you first started d2d.

For most customers, the goal is to keep backups on disk long enough to meet most recovery requests. And more and more of these customers want to be able to maintain backup on disk throughout the Data Retention window, completely excluding tapes.

Conclusion: If green it or energy consumption is taken into account, the virtual tape library vendors who are not able to provide some form of energy-efficient functionality or technology are not included in the D2D discussion.

D2D Product Type: Large-scale inactive disk array (MAID)

Electrical energy consumption: about 7 to 28 watts per TB