Feature

Storage protocols battle it out for the data centre switching crown

There used to be only one SAN protocol: Fibre Channel. Now there are several, with iSCSI, Ethernet and Fibre Channel over Ethernet (FCoE) vying to be king of the storage protocols in the data centre.

It’s a changing market, as Fibre Channel -- itself available in various bandwidths -- is challenged by the newcomer storage protocols, with this fluid situation reflected in the hardware products -- switches, etc -- that are a key component in the data centre.

In this article we will look at the products available from the three market leaders in storage switching -- Cisco, Brocade and QLogic – and assess their storage protocols strategies at this major fork in the road.

Reflecting the new, diverse landscape, products available from these vendors offer new options to storage administrators, including various speeds and the chance to converge multiple storage networking protocols within single devices.

The storage protocols market landscape

In today’s data centres, Fibre Channel is still the de facto king of storage connectivity, with Brocade and Cisco dominating the Fibre Channel SAN switch market, almost equally dividing about 90% of market share in the second quarter of 2011 by revenue, according to Dell'Oro Group.

QLogic, by comparison, has very little of the Fibre Channel switch market and is fighting for the remaining 10% with other smaller vendors. QLogic instead leads the field when it comes to server Fibre Channel and FCoE adapters -- taking 54% of total market revenue share, according to reports from Dell'Oro Group and another industry research firm, Crehan Research.

There’s an identifiable difference in bias between the key vendors. Brocade appears to be spreading its bets fairly evenly between Fibre Channel and Ethernet-converged protocols while Cisco’s product roadmap emphasises FCoE as opposed to Fibre Channel.

Fibre Channel

At its annual Tech Day summit in May 2011, Brocade announced a number of new 16 Gbps Fibre Channel products. The DCX 8510 Backbone, for example, offers 384 16 Gbps ports or 512 8 Gbps ports and, like all Brocade’s directors, can add FCoE support via an optional blade. The same event also saw the launch of the Fibre Channel-only 6510 Switch, which offers 48 ports that can be configured to run at 2, 4, 8 or 16 Gbps, plus the 1860 Fabric Adapter, which supports Fibre Channel and Ethernet for protocols such as FCoE, iSCSI and TCP/IP.

Cisco currently offers Fibre Channel systems that operate at 8 Gbps, in its MDS 9000 director switch series. Cisco has not taken Brocade’s approach of continuing to increase speeds on products dedicated to Fibre Channel. The vendor has stated that it sees purely Fibre Channel systems as having a limited future and that Ethernet-based connectivity will eventually become the new industry standard, with multiprotocol products providing the bridge to this goal. With this in mind, Cisco’s latest fabric release -- the Nexus switch series -- is a purely Ethernet-based product.

QLogic has shied away from putting large investments into Fibre Channel, preferring instead to concentrate on the convergence route with the UA5900 switch series, which also offers 16 Gbps Fibre Channel connectivity with Ethernet convergence options (see below).

Multiprotocol convergence

New developments in storage connectivity in the data centre are now focussed on multiprotocol convergence.

At the 2011 VMWorld Las Vegas event, Brocade announced the VDX 6730 Data Center Switch, a 10 Gigabit Ethernet/Fibre Channel switch that allows direct interoperability between Fibre Channel- and Ethernet-based fabrics. Two models are available -- the 32 and the 76 -- offering capacities of 24 and 60 Ethernet/SFP ports, respectively. Brocade claims 600 nanosecond latency on translation between Ethernet and Fibre Channel, with switching bandwidth of 896 Gbps for Ethernet and 256 Gbps for Fibre Channel ports on the VDX 6730 76. Ports can be scaled from 16 to 24 on the VDX 6730 32 and from 40 to 50 or 60 on the 76, allowing a lower initial investment with scope for expansion.

Since 2009 Cisco has offered the Cisco MDS 9509 Multilayer Director switch, which offers a home to the full range of MDS 9000 Switching Modules, including various port counts and bandwidths of Fibre Channel, FCoE, IBM Fiber Connectivity (FICON), iSCSI and Fibre Channel over IP (FCIP), and allows integration between all modules in the host fabric. The Cisco MDS 9513 offers 8.4 Tbps of system bandwidth and up to 528 1, 2, 4 or 8 Gbps Fibre Channel ports in a single chassis or up to 1,584 Fibre Channel ports in a single rack.

QLogic has concentrated on a move into the converged switching market with the UA5900 switch series, which provides 4, 8 and 16 Gbps Fibre Channel and 1 and 10 Gbps FCoE/Ethernet device port speeds, again with full protocol interoperability as a feature.

WAN-to-SAN connectivity

With the development of private clouds and disaster recovery requirements driving data centre locations further apart, a new class of product has evolved. These products allow direct connectivity to SANs in remote locations via the WAN and convert Ethernet WAN traffic directly to Fibre Channel interfaces. They provide great benefits, not only for disaster recovery and replication purposes, but also for live storage serving from virtually any connected location.

Examples of this class of products include Qlogic’s 6100/6200 Intelligent Storage routers, which allow cross-protocol routing for 8 Gbps Fibre Channel and 10GbE/1GbE iSCSI. Cisco also features this ability in its MDS 9513, while Brocade features it in director blades for the DCX chassis.

The QLogic approach of supplying SAN/WAN connectivity in a physically separate piece of hardware could offer more flexibility for storage administrators not willing or able to make the investment in the higher-level director products from Cisco and Brocade.

Purely Ethernet?

Cisco has positioned itself in the market with its Nexus 7000 switches, which are dedicated to Ethernet convergence. These are designed to support emerging 40 Gbps and 100 Gbps Ethernet standards for storage protocols while also supporting standard Ethernet traffic.

Meanwhile, Brocade offers the VDX 6720 switch series dedicated purely to Ethernet-based storage traffic.

Summary

What used to be a fairly simple connectivity choice for storage architects with clear boundaries and pros and cons for storage protocols has become blurred.

Interoperability between storage connectivity protocols within converged devices has become the norm. As Ethernet bandwidth availability continues to increase, it could outstrip Fibre Channel’s ability to keep up, and although this market is still very strong, the lower cost, higher performance and flexibility of Ethernet-based technologies could eventually win the day.

The three major vendors focus on protocol interoperability, and convergence provides a way for storage professionals to test the water with new connectivity options and facilitate a migration strategy between them.

Looking at the current state of products in the market, it can be assumed that this is a manufacturer-led strategy designed to move the market away from the currently accepted industry standard of Fibre Channel connectivity towards Ethernet as the primary storage networking technology of the future -- albeit with differing paces towards this goal depending on the vendor.


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This was first published in October 2011

 

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