Grueling performance testing exposes weaknesses in Cisco, HP switches
As data center managers consolidate and virtualize their servers, the next order of business becomes moving all that traffic. Enter top-of-rack data center switches that offer speed, scalability, redundancy, virtualization support and other features not available in garden-variety Ethernet switches.
How we tested the switches
This test analyzes switches, each sporting at least 24 10Gigabit interfaces, from Arista Networks, Blade Network Technologies, Cisco, Dell, Extreme and HP. We compared these products 10 different ways and subjected them to three months of grueling performance tests.
While each offered some standout qualities, we're singling out Arista's DCS-7124S and Blade's G8124 as top picks. With the best combination of features and performance – especially in the areas of latency and jitter – both switches earn Clear Choice awards. The Dell and Extreme entries also fared well.
The biggest surprises came from Cisco and HP. Cisco's Nexus 5010 is the only switch tested with a complete story on data/storage convergence, and its lengthy features list includes some outstanding virtualization capabilities. But high latency, usability gremlins and multicast leakage all hampered the Nexus 5010 in this test. HP ProCurve's 6600-24XG was only a modest performer. Although it was tops in media access control (MAC) address scalability, it was the only switch not to offer line-rate throughput, either for unicast and multicast traffic.
To help compare switches, we asked vendors to complete an extensive features questionnaire (see results). While vendors responded to more than 100 questions, we'll focus here on the major differentiators.
First, though, it should be noted that we decided not to compare vendors on price because actual pricing varies so much from list price.
Comparing basic features
The Arista, Blade and Cisco switches accept both gigabit and 10G Ethernet transceivers, a useful feature as data centers migrate from the gigabit connections found in the majority of servers today to 10G links which are likely to appear in the next year or two, especially as these begin to be embedded on server motherboards.
Cisco's Nexus 5010 is the only switch tested that offers native Fibre Channel interfaces and full Fibre Channel over Ethernet (FCoE) support. Fibre Channel options include 2G, 4G and 8G versions. All other switches can forward FCoE traffic, but that's a bit like saying an Ethernet switch supports IPv6 even though it's unaware the frames it forwards contain IPv6 headers.
All switches support redundant power supplies, and all except Extreme's offer redundant fans. The Arista and Blade designs also offer redundant out-of-band management ports. Fans in the Arista, Cisco, Dell and HP switches are hot-swappable.
Airflow is a concern in data centers, and vendors take differing approaches to keep their switches cool. The Arista, Blade and HP switches can be configured to blow air from front to back or vice-versa, depending on whether the switch faces a hot or cold row. Cisco's switch also reverses the orthodox design so that interfaces are at the back of the switch, alongside the power supplies; Cisco says this minimizes clutter.
Although data center switches that connect virtual machines will operate mainly in layer-2 switching mode, many network designs involve at least some layer-3 routing. In this test, all devices except Cisco's Nexus 5010 can route packets between subnets, either statically or using open shortest path first (OSPF). The Blade, Dell and Extreme switches also support OSPFv3 for routing of IPv6 packets.
Data center switches support failover protocols on server and inter-switch links that not only boost uptime but also may eliminate the need for other redundancy protocols such as spanning tree.
For both server and inter-switch connectivity, all switches support the use of link aggregation to bond multiple physical connections into a single logical link.
Some vendors go beyond this with supplements or replacements for spanning tree on inter-switch links. Arista's multiple link aggregation (MLAG) technology allows active/active, multi-homed connections for server and inter-switch connections, both using standard link aggregation control protocol (LACP). Blade Networks offers HotLinks, an active/passive redundancy mechanism for inter-switch links that works with or without spanning tree.
Cisco's Nexus switches offer Virtual Port Channel (VPC), which allows definition of logical server and inter-switch links that encompass multiple physical ports. Extreme's Summit x650 supports standards-based Ethernet Automatic Protection Switching (EAPS) for active/passive failover between switches, while the HP ProCurve switch uses a proprietary active/active mesh protocol to balance loads with upstream switches.
Arista's MLAG offers the twin benefits of being standards-based (it uses LACP and thus should work with any other device that supports link aggregation) and operating in active/active mode. Of the proprietary mechanisms, Cisco's VPC also offers interesting potential for carving out multiple virtual switching and routing domains within or across multiple Nexus switches.
To read the rest of David Newman's detailed review, click here: Storage/data convergence: Cisco stands alone
Network World gratefully acknowledges the test equipment vendors that supported this project. Spirent Communications supplied its Spirent TestCenter Hypermetrics 10 gigabit Ethernet test modules for this project, along with extensive engineering and logistical support from Mark Hall, Gary Hansen, Mike Kanada, Michael Lynge, Himesh Mehta, Paul Mooney, Timmons C. Player, Howard Turner and Jurrie Van Den Breekel. Thanks too to Fluke, which provided Fluke 322 and 335 clamp meters for measuring power consumption.
Newman is a member of the Network World Lab Alliance and president of Network Test, an independent test lab and engineering services consultancy. He can be reached at firstname.lastname@example.org.
Newman is also a member of the Network World Lab Alliance, a cooperative of the premier reviewers in the network industry each bringing to bear years of practical experience on every review. For more Lab Alliance information, including what it takes to become a member, go to www.networkworld.com/alliance.
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