Public institutions are among the most budget-conscious IT spenders. In that regard, the University of Vermont (UVM) (Burlington, VT) is no different. That's why, when it needed to upgrade its storage resources, the university decided to deploy its first SAN (storage area network). Traditionally, UVM had added capacity by purchasing additional direct attached RAID (redundant array of independent disks) storage. However, the flexibility and scalability of SAN-based storage overrode its higher price tag. Says Mike Austin, senior system programmer at UVM, "There's a threshold where it becomes more cost-effective to buy one high end SAN and attach multiple servers to it rather than buy separate, less expensive midrange arrays for each server."
In addition to the cost issue, the IT staff was facing the capacity limitations of having storage inflexibly tied to particular servers. "We were implementing increasingly strict policies about how much disk space users could have, and we weren't comfortable with that," Austin admits. Plus, data growth was on the march, pushing throughput to its limits - and beyond. "Our disk use over the last few years has grown from 500 GB to approximately 5 TB," Austin says.
Push Data Down Multiple Paths
Fortunately for UVM, its SAN implementation didn't have to accommodate a high degree of server sprawl. While UVM relies on more than 80 servers to support its application infrastructure, it had direct attached storage on only a core group of six file servers. Over the LAN, the other servers had been accessing data from the core servers, on which large disk arrays stored 90% of the university's data. Three of those core servers were in particular need of more storage, so UVM moved them to the SAN. Providing disk storage for those servers is SANnet 7128, a complete "SAN in a box" solution from Dot Hill (Carlsbad, CA).
Because the SANnet unit comes with four built-in Fibre Channel hubs, each with four ports, UVM did not have to buy external SAN switches. Instead, it simply dual-connected the three servers across ports on different hubs. "Since each server is connected to two hubs, if one hub fails, the server is still connected to the SAN," Austin explains. "SANnet runs software with path failover capabilities that protects the data path if a controller crashes or if someone mistakenly pulls a cable."
In addition to giving UVM's core applications high availability, the SAN also brings scalability. The rack-mounted SANnet 7128 comes standard with 10 disk drive slots and 2 RAID controllers. Additional 10-drive drawers, managed by the base unit's controllers, can be chained together. "We've scaled the SAN to 40 drive slots, and it currently handles about 3 TB," says Austin.
According to Austin, the SAN has enabled UVM to more than double the throughput on its largest server. And, it has made storage management less worrisome. "For the most part, I/O [input/output] transactions have been hands off," says Austin. "Now, the amount of time we spend managing storage is minimal - at most, two hours per week."