Cisco Goes 4-Gig & Big

SAN DIEGO -- Storage Networking World -- Cisco is ready to roll with its MDS 9513, a 528-port director with 4-Gbit/s Fibre Channel support.

It's been more than three years since Cisco first disclosed plans for the box. (See Cisco's Sales Strategy Unclear.) Paul Dul, director of product management for Ciscos Fibre Channel switches, says he expects qualification from major storage vendors -- EMC, Hewlett-Packard, Hitachi Data Systems, and IBM -- to begin next month.

Along with the MDS 9513 chassis, Cisco launched new four new plug-in modules: 12-, 24-, and 48-port cards that support 4-Gbit/s, and a four-port 10-Gbit/s module for inter-switch links and SAN extension.

The new cards, as well as Cisco's existing cards, are forward- and backward-compatible with Cisco's three director chassis, including the ones predating the MDS 9513.

The modules expand the port capacities of the directors. The 48-port cards bring the port capability of the MDS 9509 from 224 to 336 ports, for instance, and the MDS 9506 from 128 to 192.But there is a catch with the 4-Gbit/s support. Only the new 12-port cards are full-rate 4-Gbit/s modules. The 24-port and 48-port cards are oversubscribed, which means each port will not send data at the full 4-Gbit/s rate.

Because Cisco uses oversubscription and the ports share bandwidth, all the Cisco directors support only 132 fully subscribed 4-Gbit/s ports. The new 24-port card is oversubscribed at a 2-to-1 ratio, and the 48-port module is 4-to-1 oversubscribed.

Oversubscription is an old source of debate for switch vendors. (See Cisco: Oversubscribed by Design.) Cisco claims oversubscription saves users money by letting them use less bandwidth for applications that don't need full bandwidth. Cisco's previous 32-port cards are oversubscribed, but not its 16-port cards.

Brocade claims it does not oversubscribe, but its 32-port card has twice as many paths going into the switch than coming out and is susceptible to congestion that would have the same effect as 2-to-1 oversubscription. Brocade says its SilkWorm 48000 supports 256 ports at full-line 4-Gbit/s, but that's not the case when more external servers than internal servers are accessing the card.

McData does not use oversubscription on its current directors.Dul says the port-count of the MDS 9513 is more valuable than the extra bandwidth now. “We think the density is very significant,” Dul says. "Being able to put more ports in a system makes for compelling economics.”

Cisco has been slow to move to 4-Gbit/s rates. It brought out a 20-port, 4-Gbit/s switch through an OEM deal with QLogic last October, but Dul still thinks most customers can still get along fine at 2-Gbit/s.

“There are very few technical applications that can take advantage of 4-Gig,” he says.

Still, Cisco has been widely criticized for being the last of the director vendors to issue a big, 4-Gbit/s switch, even though the MDS 9513 was supposed to be part of Cisco’s initial move into Fibre Channel switches. (See Cisco 4-Gbit Director MIA.) As Dul indicates, the company's spin is that it is not late, but just on time with extra ports and bandwidth that weren't called for by customers before.

The MDS 9513 now puts Cisco ahead of Brocade and McData on ports, and between its rivals on 4-Gbit/s capabilities. Neither Brocade nor McData has directors with more than 256 ports. However, Brocade has a big lead in 4-Gbit/s -- it started shipping a 4-Gbit/s director last August and claims to have 1,000 installed in customer sites. McData claims it will demonstrate a 140-port director running 4-Gbit/s at SNW this week, but 4-Gbit/s capability for its 256-port i10K isn't expected until late this year.As for 10-Gbit/s ISLs: McData has them; Brocade does not.

So, is Cisco late to the party, or right on time with its grand entrance?

At least one analyst thinks they're on time with port counts. "It made sense that they held off when they did," says David Freund of Illuminata. "There wasn't enough of a market then. Now the sweet spot seems to be 256 [ports], and they're ahead of that."

Carl Follstad, manager of data management services at the University of Minnesota, also apparently sees things Cisco's way. The university has deployed six MDS 9509 directors as part of its new SAN, but Follstad can't wait to get his hands on the MDS 9513 because of the extra ports. (See University of Minnesota.) "We will be buying two this fall. I need that expandability," he says. As for 4-Gbit/s, "I don't need it right now."

Dave Samic, senior network analyst at FirstMerit Bank in Akron, Ohio, says he's interested in features such as Cisco's IP services module and inter-VSAN routing, but he has ports and bandwidth to spare with his MDS 9509."There's a lot of ports in that new switch," Samic says. "I'd like to have a big switch, but we have plenty of space left."

As for the oversubscription issue, Freund says the larger port count lets customers decide if they want to oversubscribe or not. "With this bigger honking switch, Cisco's saying, 'You have plenty of headroom, don't worry about it.' Oversubscription gives some people the heebie-jeebies, but I guess it comes down to how actively you're willing to manage your network."

— Dave Raffo, Senior Editor, Byte and Switch

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