Faster speeds are no surprise in storage, but this new technology eases data management too If you think your network takes a pounding, CIO Glenn Bonner at Mirage Resorts would like to set you straight. The massive Mirage Casino and Hotel towering over the Las Vegas strip is a 24/7 rush of gambling and guests. Downtime is a foreign concept for the city as well as the computers. Every time a guest checks in or tries his luck on the slot machines, he generates a network transaction. And that data has to be stored somewhere. But like many CIOs whose data needs outgrow their networks, Bonner took advantage of an increasingly popular technology called a storage area network (SAN). Simply put, it's a set of dedicated storage devices that are linked into their own network and use the fibre-channel storage interface, which takes up where SCSI (small computer system interface) leaves off. Because it comprises both storage and networking, SAN offers enough bandwidth and speed to eliminate network transaction slowdowns, a key asset when transactional data flows around the clock. "We already saw a conflict between storage needs and transaction needs," says Bonner. "Before implementing a SAN, backing up data took an incredible amount of time, and it impinged on overall network performance. Now we can separate the storage processing from the rest of the network and back up our data without interfering with our transaction needs." GartnerGroup (US) predicts that by 2001 more than 80 per cent of the Fortune 500 will have a SAN installed. Thanks to insatiable storage appetites, data intensive market segments such as digital video processing latched onto the storage networking idea first, says Robert Gray, research manager for storage systems at International Data Corporation (US). But he adds that users in virtually all industries are taking notice. In 1998, according to Gray, users spent about $US560 million on fibre-channel storage arrays for SAN environments. This year he expects that number to triple. IDC says that by 2002 fibre-channel storage arrays will be a $US9.2 billion business, and users will spend an additional $US2 billion to $US3 billion for SANs using other interfaces.
The Ins and Outs of SANs
One of the most amazing upward curves in technology has been the increase in disk drive capacity. But at the same time, new technology was needed to transport data -- frequently in much larger files than the network had contended with before-in and out of the devices. That's how SAN evolved. The fibre-channel data transfer technology supports up to a 100MBps rate over distances of up to 10 kilometres, both huge jumps over the maximum speeds and distances supported by the latest SCSI standards. About the name: Fibre-channel technology was originally designed for fibre-optic cabling, but when the International Standards Organisation added copper cable support, it adopted the international spelling of fibre in an attempt to downplay its strict association with fibre-optics while maintaining the historical link. Fibre channel is now an American National Standards Institute (ANSI) standard.
Storage area networks can comprise any number of storage systems-RAID (redundant array of independent disks), tape backup, CD-ROM libraries or simply a bunch of magnetic disks-linked via fibre channel to one or more servers.
Users can access devices over the network's high-speed connections, even simultaneously accessing the same disk at the same time (for different files, of course). By giving data storage its own highway, as it were, users don't have to battle the server for bandwidth.
It sounds simple, but because it borrows so much terminology from networking, the product array can be confusing. From vendors such as 3Com, EMC, Hewlett-Packard, Storage Technology, Transoft Networks, Xiotech and others, you can get chassis with multiple drive bays, switches (which increase bandwidth and add communication paths between servers) and hubs (which route data to multiple users and/or devices). For CIOs like Bonner, SANs solve the connectivity, data access and bandwidth problems associated with SCSI-based server-attached storage while providing dedicated connections between storage devices and applications residing on servers. The networking analogies are appropriate, because SANs share storage data the same way server application data can be shared across an internetworked enterprise. Glenn Strachan, vice president and chief information officer at the non-profit Academy for Educational Development (AED), in Washington, DC, describes his SAN as a wheel.
A Xiotech fibre channel storage array sits at the hub of the wheel, while "spokes" of fibre-channel cabling radiate out to his servers, each dedicated to a specific process. "We can put all our user files and project data on one server and use another server for e-mail, for instance, instead of using a departmental server for both data storage and e-mail," says Strachan. "This way, we don't need to load multiple processes onto one server. This simplifies management because if we want to update an application, we can update one central server instead of eight different servers." Data Management Takes Centre Stage If you measure your enterprise data storage in terabytes, chances are you're having a hard time keeping track of it all. As your data continues to grow, the question becomes not only where do you store it all, but how do you distribute, manage and back it up, especially without affecting overall network performance? That brings up a nice surprise about SANs: While software to manage a new technology usually shows up as an afterthought, it's already available for most SAN products, handling network file control, mounting and unmounting of drives, basic security and cross-platform use of shared storage on the network. You can also view data stored on multiple devices as if it were centralised. This simplified data management (which is generally supplied by the specific vendor) is as much a draw as the technology's speed, says Keith Thibodeaux, vice president of network services at Baton Rouge, Louisiana-based United Companies Financial. "The bigger draw is the ease of adding and removing storage on individual servers" with just a few mouse-clicks; Xiotech's software, he says, lets him dynamically allocate storage.
SANs offer another advantage. Among your biggest enterprise data management headaches is backup. The process usually causes network service interruptions while information gets moved from local disks on a server to offline drives for safe keeping. But SANs can remedy this painful procedure. Instead of relegating time-consuming data backups to the dead of night or weekends, when network traffic is at a minimum, the speed of fibre-channel-connected storage networks, coupled with SAN management software's capabilities, lets IT personnel back up data almost on the fly, according to the AED's Strachan. The Xiotech software permits him to create an image of any volume or disk and backs it up in real time, not just after hours. "Because the volume is going over a fibre-channel connection, and not the Ethernet LAN, we don't have to worry about bandwidth contention," he says. Even when a server fails, a SAN can drastically reduce the time it takes to make the data available. Because you can dynamically allocate a server's storage space in an array of disks, a quick switch to another drive keeps your users up and running almost without a hitch. United Financial's Thibodeaux says time savings can be measured in hours. "Once when we had a corruption on our Microsoft Exchange server, we didn't want to take time for the traditional backup-and-restore procedure. So we allocated 50GB in the storage array to cover ourselves by creating a new volume and copied the database there. Then we fixed the corruptions and copied it back." Overall, he saved several hours by not having to recover the data from tape and restore it.
Keeping SCSI in the Storage Network
Despite these benefits, you probably don't want to make a wholesale switch to the technology simply because you have too much money invested in existing SCSI storage products. However, SCSI-to-fibre-channel bridges from vendors such as Atto Technology, Chaparral Technologies and Crossroads Systems will allow you to make SCSI tape libraries and disk arrays part of the SAN. The data centre at Dublin, Ohio-based Online Computer Library Centre houses Worldcat, the world's largest bibliographic database. The centre stores 12 terabytes of data attached to an IBM S/390 mainframe and several Tandem systems as well as systems running Unix and Windows NT. "More than half of our recent growth has been on Unix and NT and we wondered how many new tape subsystems we would have to buy," says Jerry Lynch, OCLC's director of operations. "But instead of buying new drives, we can redeploy existing S/390 tape resources to the other platforms. Some are direct SCSI-connected and the rest are connected to a SAN using fibre channel and SCSI-to-fibre bridge technologies." If you're having trouble managing your data and you're juggling storage devices from multiple vendors -- and those devices are scattered around the enterprise -- you may be ready for a SAN.
Clearly, the centralised configuration, scalability and manageability make SAN technology worth considering, especially when your stored data breaches the multigigabyte level. At long last, say users, the storage portion of a network can be managed with the relative ease of managing a LAN.
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