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For example, Brocade's SilkWorm Fabric AP is built around the so-called XPath architecture, which separates out the data and control paths. Nearly all traffic (approximately 95%) travels over the data path stream, including SCSI I/O reads and writes, block-based copy and mirror and virtualized I/O translation frames. The control path, meanwhile, manages less frequent traffic--for example, volume configuration and placement, error handling and recovery and security.
According to Dave Stevens, Brocade Communications' director of business development: "Applications tend to be bi-modal--that is, 90% of the code is performance-sensitive, but not very computationally complex, and 10% is computationally complex, but not very performance-sensitive." In Brocade's architecture I/Os get pushed down to dedicated port-level processors, while non-performance sensitive data gets crunched by a general purpose processor. This approach has resulted in approximately 60,000 I/Os per port, and near wire-speed throughput of 195MB/s.
The number of intelligent switch ports you'll need in addition to basic FC SAN ports is a function of the port performance, and the I/O and throughput needs of the hosts you want to virtualize. Given Brocade's preliminary performance specifications, five hosts generating a total of 50,000 I/Os could be pooled with a single SilkWorm Fabric AP port.
|Bottom line: easier management|
Ultimately there's one very powerful argument for running storage services in the network: to simplify management.
Just take a look at managing licenses for your volume management software. Assuming price is not a factor, "as an administrator, would you rather manage licenses for 50 volume managers running on the host, or just one in the network?" asks Jeff Silva, VP, strategic planning, Maxxan.
Centralized management is one benefit that isn't lost on Chas Peterson, director of hosting at Sprint, which is evaluating Sun's 6300 family: Its 6120 arrays, as well as the 6320 management station, both precursors to the first standalone product based on Pirus technology (the 6920) due out in Q3 of this year. As a hosting provider, Peterson appreciates the way it can dedicate a 6120 array to individual hosting customers, but centrally manage the arrays.
And it's not just that management is simpler with network-based services--it's downright easy, says HP CASA user Mark Deck, director of infrastructure technology at National Medical Health Card Systems, Inc. (NMHC), a pharmacy benefit manager in Port Washington, NY. The virtualization provided by CASA "has done to storage management what Windows did to servers--click here, click there and you're done," Deck says.
"With 15 minutes of training, I was carving up LUNs," Deck says. "For me, who doesn't do much hands-on work anymore, it was pretty amazing."
NMHC is using CASA to virtualize its midrange SAN array, the HP Virtual Array 7400, which Deck says translates directly into lower total cost of ownership, "because I don't need to have a genius managing this thing--I can teach pretty much anyone to manage it."
Improved management is also what Scott Thomas, director of discovery IS at pharmaceutical firm AstraZeneca R&D Boston, Waltham, MA, hopes to get out of Sun's N1 data platform. Currently, AstraZeneca has 19TB of capacity on Sun T3 arrays, connected to Sun (QLogic) switches.
"Supporting a fast-paced scientific research environment requires us to continually configure storage and computer systems for new projects and experiments, which is very costly," Thomas says. "By centralizing storage provisioning and improving our ability to provision storage capacity, Sun's virtualization may allow us to reduce the cost of support."
But all this performance comes at a cost. Brocade's Stevens estimates a 2.5X per port cost out of the SilkWorm AP, but Randy Kerns, a partner at The Evaluator Group, Greenwood Village, CO, expects it to be more like 5X.
But that's just the price of the port--not the price of the software running on top of it. It's not clear how the software will be priced. For example, if you ran Veritas' volume manager on Cisco's switch, who would you make the check out to? Cisco? Veritas? A combination of both? Furthermore, how is the software priced? As a site license, or according to the total number of virtualized hosts? Perhaps you'd be paying for total capacity? For the time being, "there are a variety of different routes to market," says Kris Hagerman, Veritas senior vice president of strategic alliances.
No matter how low the price per port goes on an intelligent switch, it will be tough for it to drop as low as a PC. Conseco's Lucero runs DataCore software on $6,000 PCs with 6GB of cache, and he, for one, won't be buying an intelligent switch. "I'm going to spend a lot less money" on appliance-based software, "and get just as much out of it."
So, when will all this goodness arrive? Maxxan's MXV320 is in customer trials, but that's about as close as an intelligent switch has gotten to market. Most vendors talked vaguely about Q3 or Q4 of this year, but among analysts, that's seen as optimistic. "Nobody's going to make a dime off of intelligent switches this year," says The Evaluator Group's Kerns.
Furthermore, ramp up will be slow, and "vendors are at very different levels of sophistication and delivery," Kerns says. That in turn will "create a lot of confusion and disillusionment among potential customers." For the time being at least, "the appliance model is easier for people to swallow."
Past history suggests that's not the end of the story. Back in the mid-'90s, for example, when the Web was just coming on to the scene, IT managers found that their Web servers couldn't handle the load, recalls Peter Wang, CTO at iSCSI storage vendor Intransa, San Jose, CA. That led to the development of appliance-based load balancing software from the likes of Alteon and Arrowpoint, later acquired by Nortel and Cisco respectively, and integrated into high-end chassis switches.
The current trend of moving storage services to the network, is therefore, "something that all networks go through," says Mark Davis, senior VP of marketing at Milpitas, CA-based Candera, a start-up developing a so-called network storage controller. "It happened to the telephone network, it happened to IP--it's the natural evolution of the architecture."
This was first published in June 2003