Today, StoneFly's synchronous mirroring lets the backup SAN take over if Nancy's primary SAN fails, because data is written to both SAN segments simultaneously. Working closely with StoneFly's engineers to beta test the dual SAN architecture, Nancy's first moved its Microsoft Exchange 2003 data to the mirrored SAN, then added data from its QAD MFG/Pro ERP (enterprise resource planning) application, which uses about 500 GB of the 3.2-TB SAN. Since then, Nancy's has moved other data to the SAN, including data from its Cisco Unity IP voicemail system and, most recently, its new RFID inventory system.
Cost was a major reason for Nancy's choice of the StoneFly iSCSI environment. The small, privately held company had a tight budget, so not only was a separate disaster-recovery site out of its price range, but so was a Fibre Channel SAN. Nancy's went with a dual IP SAN architecture on-site, which was half the cost of a Fibre Channel SAN. "We know the IP SAN is not as powerful as a Fibre Channel SAN [in terms of speed], but in our environment, it's good enough," Choy says. Nancy's iSCSI SAN runs on a Gigabit Ethernet backbone, about half the speed of Fibre Channel, which can run anywhere from 2 Gbps to 4 Gbps.
The need for a SAN became clear when Nancy's installed Microsoft Exchange 2003, along with Active Directory. The company's DASD (direct-access storage device) architecture couldn't support the fault-tolerance requirements of the Exchange implementation. Nancy's had already bought additional servers for Exchange 2003, and the IT group was migrating Nancy's ERP application from HP-UX to an Intel-based Linux platform. The company had a choice: Add more DASD or build a SAN.