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With the proliferation of virtual tape libraries within storage environments, storage managers face an increased number of decisions in regards to managing and cataloging the transfer of data to tape.
As disk libraries become the primary backup target for near-term data recoveries, storage managers are exploring new ways to exploit tape's strengths: high capacity, low cost and mobility. Disk is the best medium for fast backups and recoveries, but tape is often the best option for long-term data storage and retention. Companies continue to use disk and tape in their backup process, but managing both media creates issues such as:
- Compression algorithm differences in disk and tape libraries
- Encrypting and decrypting backed up data
- Keeping data on specific media to meet application recovery point objectives and recovery time objectives
- Managing size differences between virtual and physical tape cartridges
- Optimizing data placement based on power savings or energy costs
- Reconstructing deduplicated data before moving it to tape
- Scheduling data movement so it doesn't impact backup windows
- Updating and protecting the backup software catalog
Although some virtual tape libraries (VTLs) include an option to manage data movement from disk to tape, most VTLs leave it to the backup software to initiate data movement and track where data is stored. VTLs' roots for managing disk and tape are found in systems originally designed for mainframe backup such as Sun Microsystems Inc.'s StorageTek Virtual Storage Manager and IBM Corp.'s Virtualization Engine TS7700. These systems were among the first to offer a disk cache to store backed up data. But these systems work only with mainframe OSes, support only FICON connections and often have prices starting in the hundreds of thousands of dollars.
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