EMC VNXe 3100 performance check

A simple IOmeter test across six virtual machines, two iSCSI volumes, and five 15,000-rpm SAS disks in RAID5

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Given that I had only five active high-speed disks, a full performance test of the VNXe wasn't really possible, but I wanted to make sure the unit wasn't obviously subpar. (See the full review, "EMC VNXe 3100: Sweet entry-level NAS and SAN.") Although I attempted to wring the most I could out of the array, I'm certain there are optimization steps that could improve the results -- and likely scalability issues that might decrease them.

To provide a basic workout, I configured two iSCSI servers on the VNXe, each bound to one of the two storage processors and attached to each of the active NICs on their respective controllers. Then I created two VMFS volumes, one on each of the two servers. The three attached vSphere hosts were then configured to use round-robin load balancing across both of their dedicated iSCSI NICs to all four of the VNXe's active interfaces, effectively eliminating any of the network interfaces as a bottleneck.

Next I deployed six virtual machines -- spread two apiece across each of the three vSphere hosts -- and attached an unformatted 10GB VMDK to each VM. These VMs were split three and three across the two iSCSI volumes, providing an even load distribution across both controllers. I then used IOmeter to run tests across all six VMs. Although I ran a lot of tests, the key one for me was a completely randomized 60 percent read and 40 percent write test using a 4KB block size across the entire disk, bombarding the same five physical 300GB 15,000-rpm SAS disks with a very difficult OLTP workload (one unlikely to be found in nature). A second test involved a much easier 2MB sequential read test to evaluate overall data throughput.

The result was that the six VMs were able to achieve a total of 862 IOPS in the OLTP test, or about 172 IOPS per active physical disk and a little over 100MBps versus the sequential read test. Overall, that's a pretty decent result for a set of five disks in a RAID5 configuration. However, both tests pushed the CPU utilization on the VNXe's storage processors beyond 70 percent. Given that I didn't have more high-speed disks to test with, I couldn't evaluate how quickly CPU bandwidth would become a limiting factor, but this is one of the significant differences between the VNXe 3100 and 3300 and something to bear in mind when choosing between the two.

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