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Spectra Logic took a different approach to support backup software on its nTier family. Because nTier runs on Windows Storage Server 2003, admins may install any backup software that runs on the Windows OS on an nTier Series disk library. Admins may configure the backup software to back up data directly to the disk cache on the nTier and then copy or move the data to any disk or tape library that's external to the nTier using the installed software.
Here again problems can surface. Because the backup software server must handle data movement from the VTL to the tape software and back again, the backup software needs to insert itself into the data path. Server performance issues can emerge as the amount of backed up data increases or as data is moved from disk to physical tape, which can impact backup and restore windows. Although backup software media servers external to the VTLs can be upgraded to meet those requirements, this task becomes complicated when upgrading backup software media servers that reside within VTLs.
Leaving the management of backed up data on disk entirely up to backup software doesn't completely alleviate other problems that may arise after using disk over time. Dave Kenyon, Sun's VP of storage marketing, finds that backup software does a "lousy job" of managing disk in VTLs because it provides no method to defragment disks or control access to data on a VTL. But he recognizes that using disk as a primary means for recovery with backup software is becoming a prerequisite for firms. "Companies are really screwing themselves if they use tape as their primary means of recovery," he says.
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