4K Random Read/Write
We precondition the P420m for 9,000 seconds, receiving reports on workload performance every second. We plot this data to illustrate the drives' descent into steady state.
The dots signify IOPS performance every second during the test. The line through the data scatter represents the average performance during the test. This type of testing presents standard deviation and maximum/minimum I/O in a visual manner. High-granularity testing can give our readers a good feel for the latency distribution by viewing IOPS at one-second intervals. This should be in mind when viewing our test results below. We provide latency charts for further granularity below.
This downward slope of performance happens very few times in the lifetime of the device (by some estimates only .04% of the SSD's life). This is typically during the first few hours of use, and we present the precondition results only to confirm steady state convergence.
Each QD for every parameter tested includes 300 data points (five minutes of one second reports) to illustrate the degree of performance variability. The line for each QD represents the average speed reported during the five-minute interval.
4K random speed measurements are an important metric when comparing drive performance, as the hardest type of file access for any storage solution to master is small-file random. One of the most sought-after performance specifications, 4K random performance is a heavily marketed figure.
The P420m comes out of the corner swinging, beating the SLC-powered P320h from QD32 to 256. The P420m averages a massive 734,219 IOPS at QD256. The P320h does not disappoint either, with an average of 711,962 IOPS.
Our read latency chart illustrates the minimal increase in latency as we reach the higher queue depths with both drives. The P420m provides lower latency in read access, while the P320h experiences some turbulence at QD16. The excellent performance at higher QD comes from the parallel architecture of both drives.
Garbage collection routines are more pronounced in heavy write workloads. This leads to more variability in performance.
The P320h leverages its SLC to provide a much higher score than the P420m, though it does experience some minor variability at either end of the spectrum. The P320h averages 206,543 IOPS at QD256, while the P420m lags behind with an average of 113,749 IOPS. This is well above the rated 95,000 IOPS in steady state.
Both SSDs provide remarkably consistent performance in heavy write workloads.
The write latency shows the P320h enjoying a significant latency advantage in this random write workload, primarily due to its SLC NAND.