Storage Management Strategies for the CIO
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The new generation of tape drives or "super drives" such as LTO, Super DLT, AIT3 and Super AIT will have a dramatic affect on library automation (see "How new generation tapes change libraries" below). The increased cartridge capacity and transfer rate performance of super drives will increase the density and reduce the size of libraries, which will need fewer slots and less media.. That will help maintain tape's 60-fold cost advantage over disk, while providing faster data access to enhance applications
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On the downside, super drives are not designed for the high duty cycles of the enterprise market. Enterprise class drives like StorageTek's 9840/9940 and IBM's 3480/90 should be used where duty cycles exceed 50%.
Tape libraries are great in SANs
Currently, the killer application for SANs is backup/recovery. Today, most SANs are connected by FC. The FC option on a tape drive costs more than SCSI. FC tape drives are needed in high-end library applications. Until the FC option cost comes down, it's less expensive to use routers and bridges to support multiple SCSI drives in a library. However, it is better to use native support than convert. Also, care must be taken to address the FC topology. For example, special ports or switches are needed that support arbitrated loop.
When using storage resource management software, make sure it's compatible with your tape library and HBAs, switches, and operating systems.Keep in mind that testing should be down to the firmware level. Don't mix and match - use tested, validated configurations. Once you arrive at a stable configuration, your tape library can aid in:
Serverless backup. Most backup software ISVs allow the tape drive to be the initiator in the SAN. Backup is much faster through a host and doesn't degrade the network.
Disaster recovery. SANs can be bridged or linked over large distances by iFCP, FCIP and soon, iSCSI. Even if you have redundant RAID, snapshots to a tape library are required as there are too many single points of failure such as software corruption, viruses and sabotage. Using the right backup software, a SAN can also split or duplex the write to a remote location.
SAN management and virtualization. Used to reduce the complexity and proprietary nature of SAN solutions. Tape, disk and memory strengths are blended and used proportionately to reduce cost. Tape is represented as an image on disk and then tapes are completely filled using volume stacking. StorageTek and IBM are the leaders in this market. SAN virtualization will become important.
Tape striping or redundant array of inexpensive taped (RAIT). This approach works for high bandwidth applications such as telemetry and seismic data. Currently, RAIT applications don't share data well in a SAN, due to EOT and other specific differences. Specialized software will be an important part of your tape library selection for this application.
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This was first published in June 2002
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