Fibre channel coming to tape libraries
By Zachary Shess
While tape library vendors don`t expect full implementation for another year or two, they are beginning to leverage the speed, device connectivity, and longer cable distances of the Fibre Channel storage/network interface. Most of the leading tape library manufacturers say they plan to offer Fibre Channel connectivity later this year. One library vendor, ADIC, already supports the emerging interface through a SCSI-to-Fibre Channel bridge.
Since its introduction, Fibre Channel has primarily been associated with high speed and/or bandwidth. However, it is its device connectivity and longer connection distances that primarily appeal to tape library users. As they have done with many new technologies, large IS departments managing mission-critical and high-volume environments will be the first to marry tape and Fibre Channel. Remote vaulting, and applications that require attachment of several tape drives and/or libraries to a network, are the most likely candidates. "The promise of Fibre Channel is that you can put a single, 100MBps wire to your tape library with a single host bus adapter," says Frank Berry, director of business development for ATL Products. "From a cabling standpoint, it`s also much cleaner."
The utilization of multiple tape libraries in large networks, coupled with increased performance, often results in bottlenecks with the SCSI interface. "Our DLT libraries run 5MBps native and 10MBps compressed. And our midrange libraries have seven drives. So that`s up to 70MBps, which will saturate multiple SCSI buses. It requires tying up multiple host bus adapters in your server," says Berry.
"Performance is important because a SCSI bus gets pretty saturated by only a couple high-speed DLT drives, for example," according to Gene Nagle, product marketing manager for Overland Data. "So you end up needing multiple buses, and then do you connect them to one server? Multiple servers? How do you get the data from server to server? Your connectivity becomes very complex, and Fibre Channel holds the promise of simplifying all that."
Steve Scully, business line manager for Exabyte, agrees that Fibre Channel`s ability to connect to multiple tape drives helps solve connectivity issues. "It`s not a performance issue if you look at the library strictly as a backup device. But as drives get faster, in clustered environments users will be doing more near-online applications, and that`s when the performance attributes of Fibre Channel will become important."
Using Fibre Channel in consort with tape backup devices will be especially useful in disaster recovery and remote vaulting scenarios, vendors say, because the interconnect will eventually allow cable distances of up to 10 kilometers. "One of the nice things about Fibre Channel is that, when you get the infrastructure set up, you can run data to a device that is down the hall, or 1,000 meters away, and it`s just like the device is alongside your desk," says Steve Whitner, marketing director at ADIC.
Fibre Channel tape drives are still one or two years away. However, tape library vendors and OEMs are providing Fibre Channel networking options through various conversion methods. For example, ADIC, ATL, Exabyte, Emass, and Storage Technology all either have SCSI-to-Fibre Channel conversion units, or are currently developing them. Most vendors agree that there is some performance degradation from using bridges, routers, or hubs, but that for now there is no other option.
"All the OEMs want to talk about Fibre Channel," says ATL`s Berry. "Generally speaking, they aren`t really considering any new products unless the vendor has some type of Fibre Channel interface strategy."
"OEMs are talking the most about Fibre Channel," agrees Exabyte`s Scully, "It`s mainly the system vendors that are trying to build clustered environments with multiple servers and RAID devices. They also want to put the backup device in the same cluster."
Storage Technology is taking a different approach to providing Fibre Channel connectivity. For more than a year, the company has been developing a Fibre Channel interface that will be portable across StorageTek`s various products. Company officials say they are willing to wait a little longer than some of their competitors to make sure the Fibre Channel connectivity will work effectively in both future and legacy applications.
"Our plan is to develop the fundamental Fibre Channel architecture in some of our high-end tape drives, and then port that architecture to some of our NT and Unix tape drives and libraries," says Tom Haapala, marketing manager at Storage Technology, " The tape drives are the gauging item in terms of availability, and then the libraries will follow."
And, in fact, maybe there`s no reason to rush to market with Fibre Channel-enabled tape libraries. Says Ian Stewart, another marketing manager at Storage Technology, "The truth is that there`s always going to be people who will use current technology and stick with SCSI. So the migration is not going to be as rapid as the so-called experts think. There`s still a lot of work that has to be done."