FirstMerit Corp., an Akron, Ohio, bank with $10 billion in assets, has deployed storage virtualization technology from IBM to let it serve a growing number of online users. Using IBM's SAN Volume Controller, the bank has created a single pool of virtualized storage out of multiple disk storage arrays, and in the process reduced bottlenecks in application throughput and freed up storage capacity to deliver information to an expanding customer base.
The bank has experienced a 15% growth rate in the number of online banking accounts over the past year, and has also made significant enhancements in its online banking and bill payment platforms. This has placed a heavy burden on the bank's storage requirements: During that time, its storage capacity has grown from two terabytes of data to 12 terabytes.
FirstMerit had invested in an IBM DS4400 disk storage system as part of an effort to consolidate multiple directly attached storage systems. "The driving force behind launching a storage-area network was all of that direct-attached storage lying all over the place," says Dave Samic, FirstMerit's senior network analyst.
Yet, as storage requirements grew, the amount of available disk space became a bottleneck. In the RAID 5 implementation that FirstMerit was employing, only three disks' worth of addressable storage—about 280 gigabytes—was available for each application. "With a highly available app server, you start overtaxing the I/O in those three disks," Samic says.
By installing SAN Volume Controllers between the disk subsystem and the host apps, FirstMerit was able to surmount the storage obstacles and provide improvements in throughput. SAN Volume Controller essentially caches I/O requests, enabling host applications to address much-larger logical arrays; instead of being limited to three disks, I/O requests can be spread across all 14 disks in the DS4400. "When the host is talking to the SVC, its talking not to physical I/O but to cached I/O," Samic says.
What's more, the increase in I/O is linear: As a second DS4400 is added, available I/O jumps from 14 to 28 disks; with a third DS4400, available I/O jumps to 42 disks. Samic says, "As you increase the number of disks in your system, you increase your performance three-fold."