Test System and Methodology
Our approach testing storage is specifically designed to target long-term performance with a high level of granularity. Many testing methods record peak and average measurements during the test period. These average values give a basic understanding of performance, but fall short in providing the clearest view possible of I/O Quality of Service (QoS).
'Average' results do little to indicate the performance variability experienced during actual deployment. The degree of variability is especially pertinent as many applications can hang or lag as they wait for I/O requests to complete. This testing methodology illustrates performance variability and includes average measurements during the measurement window.
While under load, all storage solutions deliver variable levels of performance. While this fluctuation is normal, the degree of variability is what separates enterprise storage solutions from typical client-side hardware. Providing ongoing measurements from our workloads with one-second reporting intervals illustrates product differentiation in relation to I/O QoS. Scatter charts give readers a basic understanding of I/O latency distribution without directly observing numerous graphs.
Consistent latency is the goal of every storage solution, and measurements such as Maximum Latency only illuminate the single longest I/O received during testing. This can be misleading as a single 'outlying I/O' can skew the view of an otherwise superb solution. Standard Deviation measurements consider latency distribution, but they do not always effectively illustrate I/O distribution with enough granularity to provide a clear picture of system performance. We use histograms to illuminate the latency of every single I/O issued during our test runs.
We measure power consumption during test runs. This provides measurements in time-based fashion, with results every second, to illuminate power consumption behavior. This significantly affects the TCO of the storage solution. We also present IOPS-to-Watts measurements to highlight the efficiency of the storage solution.
We conduct our tests over the full LBA range to allow each HDD to highlight its average performance. Short stroking can increase performance at the loss of capacity. The Seagate v7 series only comes in a capacity of 1.2TB, while the v6 series offers similar performance but smaller capacities of 300, 450, 600 and 900GB. The first page of results provides the 'key' to understanding and interpreting our test methodology.