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Enterprise backup solutions from Computer Associates International, Legato Systems, Veritas Software and others vendors have long been used for remote users. Yet, slow and spurious communication links make this an impractical solution for road warriors. At the least, centralized backup solutions need to incorporate delta change technologies like Mobiliti's iDESP and compression when transmitting backup sets over slow data lines. And, ideally, the transmission would be encrypted and capable of checkpoint restarts when connections fail. Both Veritas NetBackup Professional 3.1 and Legato NetWorker Laptop work toward these ends.

Veritas NetBackup Professional uses a single-instance data store that discovers duplicate files across mobile laptops and keeps only one version of a common OS, application or other Microsoft object in the data store. Incremental backups then transmit new files and the delta changes to modified files in compressed format. The data store maintains a complete image of the latest version of each file and the changes that occurred down to the file-block levels to reconstruct previous versions. This not only relieves road warriors from sending complete files but also reduces the amount of online storage required for distributed laptops.

Legato NetWorker Laptop also uses delta-block technology that identifies changed or new file blocks and compresses the data to reduce the transmission size. It transmits the data using 112-bit DES (Data Encryption Standard) encryption and also stores the data in encrypted form to ensure its integrity if the data center is compromised. NetWorker Laptop goes one step beyond NetBackup Professional and lets remote users restore files via the Web when the laptop is inaccessible or stolen. Because Legato co-labels and sells Connected TLM, I went straight to Connected TLM for a pilot version.

I tested Connected TLM's service rather than its shrink-wrapped software for the enterprise. The company set me up with a registration code and password to get started. This gave me administrative access to a Master Account through a Web browser where I could review account information and user activity, generate reports and download the corporate deployment kit.

Agent software can be downloaded and installed from the TLM Web site. Agents support Microsoft Windows 95, 98, NT and 2000 clients. When installing the software to my IBM ThinkPad, I entered a registration code and password and proceeded to select a pass phrase to encrypt the data sent to TLM's storage service over the Internet. After the client was installed, TLM agents loaded into approximately 140 KB of RAM.

A TLM launcher application (Cblaunch.exe) runs as a system service and starts the main program file (Cobackup. exe) for scheduled, unattended backups. Cobackup.exe is the main user interface (1.7 MB of RAM) that performs backups, retrievals and sets configuration options. It can be invoked from TLM's system-tray application, Cbsystray.exe, which also detects user logoff and prompts the user for backup prior to system shutdown. After calling Cobackup.exe, I explored the default settings for unattended backup and selected an initial backup set.

Three file-selection methods are available to remote users: automatic, manual and full system. An account administrator can set the method in a distribution package. The default file-selection mode is automatic, where the backup agent identifies files for backup based on configuration files (DefRules.dat, DefRules.fsr). The configuration files determine whether a file is a data file to be included in the backup set or an application file to be excluded. The full system method not only backs up data files but also system, application and configuration files.

I selected the same 17 MB of data backed up by Mobiliti's N/U. TLM backed it up in 24 minutes over a 31,200-bps connection; in two minutes over a DSL/cable modem service; and in 26 seconds over a 100-Mbps LAN connection. During the backups, I continued to work but with a noticeable delay. After the initial file set was created, modified files and new files placed in the directories targeted for backup were automatically scheduled for the next backup and included in a projected file set that can be reviewed on screen. For modified files, only the delta changes down to the block levels would be transmitted to the data center. Subsequent incremental backups took from three seconds to nine minutes.

Restoring files from the data center is done with Cobackup.exe by selecting a folder or file from a windows-style interface or through a Web browser. I accessed my backup sets over the Web using TLM's iRoam module. The default page welcomed me to the data center and challenged me for an account number and password. After I supplied my credentials, the Web browser displayed a Windows explorer interface to my backup sets where I could retrieve the most recent version of a file or choose from among all versions backed up.