Making a shopping list of backup features
and IBM's enterprise backup solution
This month, the Windows NT Magazine Lab concludes its in-depth coverage of backup products for Windows NT with a look at IBM's ADSTAR Distributed Storage Manager (ADSM) 3.1 backup software. We began evaluating backup products in September 1997. Since then, we've looked at solutions to help keep your data safe, and we've learned a lot about NT backup solutions. Based on this experience, we identified factors you'll want to consider before you choose a backup solution for your organization.
The most important factor in determining the appropriate backup software for your environment depends on your network's scope and diversity. First, we assume you use NT as the master operating system (OS) for your network. Second, we assume you use magnetic tape to back up data. Tape is not necessarily better than other media, but it is currently the backup software vendors' preferred medium. If you're considering using hard disks as your storage medium (there are many good reasons for using hard disks, including price and performance benefits), find out whether your backup vendor supports this option. Before we discuss network configurations further, we need to quickly look at backup strategies.
Choosing a Backup Strategy
The basic theories on the best way to oversee the integrity of an organization's critical information involve centralized and decentralized backup strategies. These two strategies are analogous to the ongoing battle between federal and state governments over who is responsible for particular operations.
The centralized model relies on massive networks and hulking robotic storage devices. Several vendors, including HP, IBM, Legato Systems, Software Moguls, and VERITAS Software, offer centralized backup solutions for organizations with more than 500 clients and servers and various OSs. All these vendors migrated their products from UNIX to NT and are experienced in the details, features, and safeguards associated with backing up terabytes of mission-critical information. However, because these vendors' products are built on years of UNIX enterprise-computing experience, configuring the products to run on an NT network can be challenging. Many vendors claim their products run seamlessly in the background once the software is running, and don't require further configuringbut don't believe them. Corporate networks are not static entities. Companies are constantly upgrading software, scrapping old machines and installing new ones, switching departments around, and adding new users to the network. In such a dynamic environment, you will need to constantly adjust your backup configuration.
The decentralized model uses the same technology as the centralized model, but on a smaller scale. Vendors such as Seagate Software, Stac, NovaStor, Barratt Edwards International, and Cheyenne offer small to midsize solutions.
NT Lab's Backup Software Guidelines
Choosing the right backup software for your network requires you to understand the features that backup products offer. We have created the following set of guidelines to help you select backup software.
Environment. The backup software you're considering must provide agents or support for all the OSs (e.g., various UNIX versions, Macintosh, OS/2, DOS, and Windows NT, 95, and 3.1) and software (e.g., Oracle, SAP, SQL Server, and Exchange) associated with your network. If the solution doesn't support the machines and software on your network, it's not a solution.
Interleaving or multiplexing. Interleaving is the ability to write multiple modular data streams from multiple client or server systems to one recording device concurrently. With interleaving, systems administrators can eliminate the network bottleneck that occurs when a tape device has to wait for data coming across the network from one machine. Without interleaving, you might need to run numerous backup operations using numerous recording devices simultaneously to meet the time constraints of your backup window in increasingly full-time networks. With a noninterleaved solution, you might have to track and move more media offsite, which can cause more headaches.
Some vendors don't offer interleaving and instead run tape devices at full throttle to achieve high performance. However, given the recent advancements in capacity and recording speed technology and the likelihood that these advancements will continue into the foreseeable future, investing in a solution that doesn't offer interleaving (especially in an enterprise environment) doesn't make sense.
Device support. Extensive device support, especially for robotic autoloading devices, is a must for enterprise-level backup software. Make sure the backup software you're considering supports your existing and future investment in storage technology.
Client-side compression. Client-side data stream compression lets you send more data to the server for backup in less time. This feature improves the overall efficiency of your backup solutions.
Centralized software distribution. With centralized software distribution in a true enterprise environment, you don't have to visit every client computer to install backup software. You can push the software across the network to each client machine from one location.
Disaster recovery. Effective and efficient disaster recovery must rank high on your shopping list. When you evaluate disaster recovery solutions, ask each vendor how its product handles hard disk partitions and recovers a failed machine; in particular, ask how the product handles NTFS and FAT file systems and their partition sizes during restores. The differences among solutions will surprise you.
Notification. A robust notification feature set including email, pager, fax, and Simple Network Management Protocol (SNMP) is highly desirable. If part of your backup routine fails, you'll want to know about the problem immediately.
Open files. The two strategies for dealing with open files during a backup operation are to skip the open file and back it up later or take a snapshot of the file in whatever transitional state it's in during the backup operation. Both methods are generally satisfactory for most networks, but they might not suffice for 24 * 7 transaction servers where lost data or a corrupt file can mean the loss of thousands of dollars. For these scenarios, you can rely on more sophisticated solutions, such as St. Bernard Software's Open File Manager, that integrate with available backup solutions. Other vendors have robust proprietary methods for handling open files. Be sure you know a company's open file management solution capabilities before you experience a problem.
Media tracking. Your data's integrity is only as good as the media you write it to. Therefore, many backup solutions let you track how many times you write and rewrite to a particular tape.
Restores. Restoring individual files and folders is the backup administrator's most common task. You don't want to have to jump through too many hoops to restore a file or folder after a backup operation.
Multiple runs. Depending on your network configuration, including the number of servers and tape devices, you might want a backup solution that lets you run multiple copies of backup software concurrently. This feature will let you collect information on specific media types without jeopardizing the backup window.