QLogic’s SANbox 5200

Logic’s new stackable storage-area network switch – the SANbox 5200 – that features 10G bit/sec interconnections begs the question of how well this architecture can stand up against a chassis full of Fibre Channel port modules.

Logic’s new stackable storage-area network switch – the SANbox 5200 – that features 10G bit/sec interconnections begs the question of how well this architecture can stand up against a chassis full of Fibre Channel port modules.

In our tests, the SANbox 5200 offered effortless installation, very efficient management and interesting features, but only middle-of-the-road performance.

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QLogic markets its SANbox 5200 under a “simplicity” tagline, a term that is fitting, given its quick-start guide and configuration wizard. The guide was easy to follow and well organized. The detail provided in the configuration wizard makes the installation process easier by giving users the necessary technical background in clear, bite-size chunks.

Once the SANbox 5200 was installed and configured, we had to connect the test gear, a process that could use some improvement. The switch’s port labels make it difficult to find specific ports. The switch supports beaconing – a diagnostic mechanism for locating a specific port in the SAN fabric – but only on a per-switch basis.

In the real world, our test gear would be replaced with host bus adapters and connections to other switches. This can pose a challenge to any Fibre Channel SAN switch because of interoperability issues that plague the SAN industry. QLogic offers an effective interoperation guide on its Web site.

After we configured the switch domain ID – a unique number that identifies the switch to the fabric – the switch required a reset for the changes to take effect. That’s not normally a problem, but SANbox Manager didn’t forewarn us, and went ahead and reset itself: All traffic on that switch unexpectedly stopped.

QLogic’s bundled management capabilities are impressive. The overarching management application is called the SANbox Manager. Its diagnostic tool belt is especially well outfitted with features such as Fabric View – a real-time monitoring application that graphs throughput and errors on a per-port basis – and a searchable, filterable, sortable event manager. However, some of the events these tools reported could offer more detailed information.

The SANbox Manager’s centralized management capability is a nice plus for monitoring a stackable switch, but the administrator still must configure the majority of settings one switch at a time. This could tie up an administrator when configuring or reconfiguring a larger deployment.

When configuring Fabric View options, the administrator has a dynamically constructed view of the fabric topology, including all switches and their inter-switch links.

The drill-down, single-switch view offers a graphical representation of the switch with individual port status. An extensive array of counters display real-time statistics on Fibre Channel control traffic and errors, and current port configuration. This feature was useful while tracking performance issues.

Most notable among the SANbox 5200’s architectural features is support on each stackable unit for four 10G Fibre Channel ports. This feature enables effective stacking, thus eliminating the need to steal from the 16 2G bit/sec ports for inter-switch links (ISL) and thus reducing the overall number of switches you need.

SANbox 5200 had another noteworthy feature called I/O StreamGuard. When a device logs onto a SAN fabric, it generates a notification of a fabric change that must be propagated to and processed by other devices, causing a small interruption to the fabric. This notification is critical when the state of a storage device changes, but it is unnecessary for hosts and servers accessing storage. I/O StreamGuard suppresses such host notifications, staving off this expected drop in throughput.

Also noteworthy is QLogic’s pay-as-you-go licensing approach for the SANbox 5200. Users can license the use of four ports at a time, allowing for more detailed scalability.

On a single-switch unit, we measured line-rate throughput, and latency results registering less than 10 microsec, when sending bidirectional traffic between port pairs (see How we did it). Under the more grueling mesh tests, however, where data from each port is sent in a round-robin fashion to all other ports, there was a performance drop-off. The worst-case test – where we tested a full-mesh configuration and pushed small frame size (60 bytes) – resulted in a 4% drop in throughput per port. But despite that, the distribution of throughput was even across all ports in every test, including the congested tests.

When a SANbox 5200 configuration grows beyond one switch unit, the 10G bit/sec ISLs are introduced into the fabric. We verified that one 10G bit/sec ISL could hit a maximum throughput of 1,255M byte/sec – just a smidgen less than six 2G bit/sec ports – while adding no more than 9 microsec of latency. The fairness of throughput distribution, and line-rate throughput between port pairs, is maintained when the same traffic streams are sent across ISLs. Also, the SANbox 5200 recovers well from an ISL failure, which requires that there were multiple paths between switch units. We clocked the fail-over time at 59 millisec.

QLogic recommends growing the switch fabric up to four stackable switch units – a total of 64 user ports. It also recommends one ISL hop from one switch to every other switch and multiple paths to all switches. This practice yields the best possible performance when redundancy between all switches is required. But it also creates an over-subscribed fabric – a point QLogic freely concedes.

We pushed the fabric to the edge with a full-mesh test and saw a 7% drop in theoretical maximum throughput for large frames and a 14% drop for small frames.

We verified the SANbox 5200 could perform a code load and activation while under load – a true differentiator for a switch in this market. We tested the switch’s ability to recover from a power failure and noted no residual problems once the switch returned to an operational state after 2 minutes, 32 seconds.

Overall, there is room for performance improvement but its simplicity and innovative features earn QLogic’s SANbox 5200 a very solid standing.