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An infrastructure that incorporates SAS switches also can be used to deploy a tiered-storage solution using a mixture of 3Gbps and 6Gbps, SATA and SAS storage devices, including spinning and/or SSD media. As many as 1,000 devices can be connected in each storage system. What's more, LSI SAS switches can be placed as far as 75 feet apart, about four times more than traditional direct-attached storage systems using passive copper cabling.
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As many as four SAS6160s can be cascaded or connected redundantly to boost bandwidth or provide fault tolerance and high availability applications in data center, managed hosting or could computing scenarios. Each of the SAS6160's 16 ports provides four 6 GB/s lanes for a total of 24-GBps bandwidth per port, and a total aggregate bandwidth of 384 Gbps for the entire switch.
The specified throughput of the SAS6160 exceeds our ability to test. Instead, we sought to verify the SAS6160's per-port transfer rate and to measure its transaction capabilities. To do so, testers prepared a server-class machine with 4 GB of DDR3 memory running the 64-bit version Windows Server 2008 Data Center and a MegaRAID SAS 9280-8e RAID controller from LSI.
We configured three SSD drives of a 24-drive JBOD as a RAID 0 array and used Intel's IOmeter to test throughput (measured in MBps) and transaction processing (in IO/s) with the server connected directly to the array. These results would become the performance baseline. Then we connected the server to the SAS6160, ran another cable from the SAS switch to the array, and repeated the same IOmeter test.
After some back and forth with LSI engineers to make sure that our IOmeter settings were in tune with the LSI MegaRAID card, we observed sustained throughput rates at around 815 MBps, and a sustained transaction rate of 3273 IOps. When connected through the SAS switch, throughput dropped by about three percent to 789 MBps, and transactions 3156 IOps, an additional latency of 12 microseconds per IO.
Next: Setting Up SAS6160
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