Narrowing the Window on enterprise backup choices

Avoid catastrophic data losses by choosing the best backup system for your data storage needs.

By Elizabeth M. Ferrarini | Posted Jun 23, 2000
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The tremendous growth of the IT industry has created an increasing demand for data storage capacity and, consequently, for better data backup services. Fueled by Internet technologies, electronic messaging, multimedia, online transaction processing, and other data-intensive applications, the enterprise backup and storage market is expected to double during the next two years, according to David Hill, storage analyst with the Aberdeen Group (Boston, Massachusetts).

The essentials of backups

"Three types of backup technology are frequently used: quarter-inch cartridge (QIC), digital audio tape (DAT), and digital linear tape (DLT). "

Data recovery tools and services do exist--but they are limited and expensive. With these products, you might be able to retrieve some of their lost data; but it is unlikely you will ever retrieve all of the lost data (especially complex applications, network configurations, customized setups, and passwords). The sudden loss of a mission-critical server that stores and maintains corporate records and data can be financially disastrous. A well-designed backup system safeguards crucial information, providing the most efficient insurance against disaster.

Developing a successful backup strategy begins with a carefully planned backup-needs analysis. The administrator first identifies the company's total backup needs and then matches those needs to the appropriate backup hardware and software. In many companies, as much as 40 percent of the data changes every month.

The ultimate goal is to back up all company data and programs so the entire system can be restored in the event of a catastrophic disaster. The total amount of data to be backed up indicates the capacity required of the drive and the media. If planned backups will be unattended, then the selected backup device must have enough capacity to hold the full amount of information that must be stored.

And in the most efficient organizations, safeguarding data on desktops is also planned for. This can be as simple as requiring (and training) users to store all data on network servers, which are systematically backed up. Only applications need be restored on the clients, a simple disk-image overlay with minimal user-specific customization can recreate the client machine quickly.

Another crucial factor to consider is the performance of the backup kit--both hardware and software. System administrators typically perform backups when user demands on the server are at their lowest. Ideally, this time period (often called the backup window) happens when user access can be restricted or the server shut down. For many companies with worldwide operations accessing their servers, no clear backup window exists. In such an instance, the administrator will have to perform the backup while the system is still in use. This procedure often leads to some degradation in overall performance. And with data in use you are never really sure of what got backed up.

Where a backup window does exist, the selected device's backup rate, together with the appropriate backup software, must be able to accomplish the task within the time available. The amount of data that needs to be backed up, along with the time available for doing it, often determines the type of media and software that can be used. To determine the required backup performance as an overall transfer rate (gigabytes per hour), simply divide the amount of information to be backed up (in gigabytes) by the backup window (in hours).

Data backup technologies

Currently, three types of backup technology are frequently used: quarter-inch cartridge (QIC), digital audio tape (DAT), and digital linear tape (DLT). The oldest and most common is QIC. QIC drives have the lowest capacities and slowest transfer speeds. They meet the half-height form factor of desktop computers, and are virtually industry-standard for standalone machines. However, with capacities limited to 1.2GB, they are not generally suitable for backing up servers with 2GB or more storage capacity--a capacity exceeded by ordinary desktop PCs nowadays.

The second most popular backup hardware format is DAT. Servers with 2GB to 8GB capacity can benefit from DAT drives. A high-density DAT tape can store up to 16GB of data with efficient compression. Like QIC drives, DAT drives also offer good value for your money. In addition to bigger capacities, they offer better reliability and, more importantly, random access to stored data.

Medium-level enterprises that have modest backup windows and budgets are ideally suited for DAT backups. Even fast-growing small businesses with increasing backup requirements might want to consider migrating to DAT at some stage from QIC, or other less capable solutions.

One of the Goliaths among backup technologies is DLT. These drives can store up to 30GB of data. The basic DLT technology has been around for a decade; Digital Equipment Corporation (DEC) first introduced it in the early 1990s. When coupled with RAID technology, arrays of identical DLT drives offer a high degree of fault tolerance and data accuracy. In addition to much higher data backup capabilities, the basic DLT design is inherently more reliable than those of DLT's counterparts from the older technologies.

In DAT and other helical scan drives, the tape is wound tightly around a drum and moves through a complex tape path, resulting in stress and abrasion to the tape and the heads. DLT tape operates at a lower constant tension and, therefore, has a longer lifespan.

Dedicated backup networks

After deciding the type of backup device, you must adopt a schedule and methodology for creating the backups. For instance, if the backup windows are small or non-existent, you may opt for a dedicated network just for backup purposes.

This dedicated network, which is completely independent of the normal LAN, has two major advantages:

  • It almost completely eliminates the need for a backup window, because the backup process can be completed while users are still logged on to the network.
  • Because a dedicated channel exists for transferring backup files, the bandwidth on the main LAN remains untouched, and the backup process does not affect performance.

This dedicated network can be constructed using regular networking cables or fibre channel cables. Of course, high bandwidth technologies like fibre channel tend to be much more expensive.

Backup software choices

Choosing the right hardware is only half the backup solution. If you don't have fully tested software to run on the appropriate platforms, even the most robust hardware setup may not be able to prevent loss of data. Like hardware, backup software is available from a number of different vendors to suit all needs and budgets. Most of the major vendors support the popular Unix platforms, Windows NT, and NetWare; if you are backing up data resources on other platforms, you may find your choice is restricted.

In most companies, the backup process occurs remotely, without human intervention. Therefore, a backup software package must be able to schedule all the tasks involved. At times specified by the system administrator, the software must initiate the backup process. It must also monitor the entire process and report any problems. If the problem relates to software (such as a conflict with another application), the package must be intelligent enough to recognize it as such and take the appropriate measures to correct it. Even some hardware problems can be fixed by good-quality backup software.

Most backup software vendors offer regular updates for their products. However, not all updates may be appropriate for every organization. Therefore, always check the quality of technical support available before purchasing the product.

Conclusion

Data backup is an integral part of any organization's IT infrastructure. Although not quite as visible as many other operations, data backup is just as important to the success and well being of any organization. As the amount of data in an organization increases, the scale of the backup solution must keep pace. As the world moves to a 24/7 Web-enabled e-commerce model, downtime for backup and restore must be kept as close to zero as practicable. Backup speed can become a critical issue for business competitiveness. //

Elizabeth Ferrarini is a freelance writer from Boston, Massachusetts.

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