Backup windows are shrinking as our Web-based economy expands and organizations do business around the clock. A major user study conducted by the Taneja Group, Hopkinton, MA, in conjunction with Storage in September 2003 showed that 67% of the respondents had a backup window of eight hours or less. (See "Plan on disk-based backup") Yet the amount of data to be backed up daily continues to mount. At the same time, businesses have adopted a zero-tolerance policy for data loss and have instituted stringent recovery time objectives.

During the past 20 years, there hasn't been much change in the way businesses perform backups and restores. But cheap disk prices, along with the commercialization of content-addressed storage (CAS)--which reduces the amount of data that needs to be protected--are fueling major changes in the way businesses protect their data.

Here's the payoff: If users choose wisely, they can improve the reliability and speed of their backups and restores by at least an order of magnitude. The Taneja Group classifies next-generation backup and restore products into the following categories (with some falling into several categories):

• Minimize disruption to the current environment
• Reduce data
• Provide continuous backup and restorability
• Eliminate tape
• Use replication technologies for backup

However, once disk is introduced into the infrastructure as a backup medium, the situation changes dramatically (see "Pros and cons of new backup and restore solutions"). Vendors such as Advanced Digital Information Corp. (ADIC), Alacritus Software, Diligent Technologies Corp., Neartek Inc., Quantum Corp. and Sepaton Inc. have developed technologies that virtualize disk arrays and emulate a tape library.

Pros and cons of new backup and restore solutions

The ADIC, Quantum and Sepaton offerings are delivered as prepackaged appliances that include disk storage capacity. Alacritus, Diligent and Neartek, on the other hand, are software-based tape virtualization products that are capable of running on a standard server platform with a variety of disk storage on the back-end.

When virtual tape is brought into the environment, the disk system acting as a virtual tape library becomes the target device for the backup server instead of the physical tape library. Otherwise, the environment doesn't change. Once the backup completes, the application servers are free to continue regular operations. Data from the secondary disk, under the command of the regular backup application--whether it's IBM's Tivoli Storage Manager (TSM), Legato's NetWorker or Veritas Software Corp.'s NetBackup--can be copied from disk to tape (cloning) or moved from disk to tape (staging) based on user-defined policies in the backup application.

Tape virtualization and emulation technologies minimize the level of disruption to existing backup procedures, policies and the underlying backup infrastructure when disk is introduced. What's more, users aren't required to purchase disk backup options from their backup application software vendor. When considering tape emulation technology, a user needs to weigh the trade-offs between more open software-based approaches and prebuilt appliance models with back-end disk capacity. Users should also confirm that the required tape library and tape formats are supported by the specific vendors.

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