In the struggle to get optimal utilization from your storage resources, you might be tempted to rob Peter to pay Paul. Suppose servers or storage devices in one part (the "Paul" part) of your infrastructure are running out of disk space for the applications they support. Why not pull storage capacity from less heavily used devices (the "Peter" part)? The move seems logical enough. But, suppose Paul and Peter are two storage boxes directly attached to two application servers on your local network. Now, the theft requires an accomplice - the LAN. Each time data needs to be moved from Peter to Paul, the LAN has to carry the load. So, what brought relief to Paul creates a burden for the LAN, decreasing network performance as data-intensive files are sent in search of space. A more effective antidote is to take the storage from the LAN and put it on a SAN (storage area network). That's exactly what US Labs is currently doing to relieve its overburdened LAN and give more work to its underutilized (and over-purchased) hardware.
Storage Space - Steal It Or Share IT?
At US Labs, the storage crunch stems primarily from the image-intensive nature of its work. As an anatomic pathology lab specializing in cancer testing, US Labs offers screening, diagnosis, prognosis, and genetic testing services to hospitals, physicians, pharmaceutical companies, and research institutions. The screening and testing machines it uses generate large digital images. For example, images produced by the machine for breast cancer screening typically require 100 MB of file space. It isn't unusual for the lab to produce more than 100 of those files per day. That's a gigabyte every 10 days - from just one machine. While machines used for other diagnostic purposes produce smaller images, they generate a lot more of them.
Before it began to migrate its storage to a SAN, US Labs often took the common approach of "throwing more storage at the problem." Each screening or testing machine had its own direct attached file server, which served as a dedicated storage unit for maintaining digital images. When a particular machine needed more storage space, the lab's IT staff would simply buy another server to attach to it. "A department might undertake a new project to study a particular type of case. We'd go off and buy a server so that it could store the images for that project," says Bob Stavrou, director of IS (information services) for US Labs. When it wasn't buying new servers, US Labs was patching storage gaps by moving data from one direct attached file server to another. "On many occasions, we reached the point where we had to steal space from this or that server," Stavrou admits.
SAN Brings Management Flexibility
Since it had been spending plenty on new storage hardware, US Labs didn't want to sink a lot more money into a SAN solution. Plus, with a small IT staff, it didn't want to build a complex, difficult-to-manage SAN infrastructure. So, US Labs purchased the SAN Connectivity Kit 1000, a starter SAN package from QLogic Corp. The kit provided US Labs with QLogic's eight-port SANbox Fibre Channel switch, multiple SANblade HBAs (host bus adapters), multiple GBICs (gigabit interface converters), fiber optic cabling, and various device drivers and software management tools.
To get started on putting storage-specific units on its new SAN, US Labs also brought in an eight-drive NexStor rackmount disk array from nStor Technologies. "We wanted an inexpensive way to begin building our SAN," Stavrou says. "With the QLogic Connectivity Kit coming in at around $10,000, the total price tag for the initial SAN rollout was only $30,000."
Thus far, US Labs has made incremental yet successful steps in migrating its data to the SAN. In addition to putting its home directory server on the SAN, US Labs already has two of its departments using the SAN-based disk array. The department that generates flow cytometry images, which each take up only three or four MB of data, is one. "Right now, the storage array holds approximately 500 GB. As we add drives and scale up to multiple TB of capacity, we'll move more of the image-heavy files over to the SAN," Stavrou explains.
Even before the major scaling efforts get underway, US Labs is realizing some of the benefits of centralized, SAN-based storage. "We've gained efficiencies in the way we manage storage devices," says Stavrou. "Since they're in a central place, we can add disks or reconfigure zones to give applications the storage they need. We can also do backups from the SAN box without having to run the backup agent on each diagnostic machine."