Performance Focus – Samsung 970 EVO 250GB, 500GB, 1TB
I'm sticking with the 'burst vs. saturated' plots here, as they do well to show both sustained performance and the more realistic (for client PC usage) burst throughputs. Caching SSDs turn in vastly different results for the two methods, especially for writes, as shown below.
1TB shows a cached (burst) write speed of just under 2.5GB/s, with sustained (saturated) writes falling off to ~1.2GB/s.
500GB shows a cached (burst) write speed of just under 2.5GB/s (matching the 1TB model), with sustained (saturated) writes falling off to ~700MB/s.
250GB shows a cached (burst) write speed of 1.5GB/s, with sustained (saturated) writes falling off to ~300MB/s. This seems low, but it is expected TLC speed for such a small capacity. Typical use will realize the 1.5GB/s for the vast majority of write accesses.
The 250GB model also sees just a slight drop in sequential read speeds when compared to the larger capacities. Nothing to worry about there, though.
Note that as we reduce the capacity, we also reduce the 970 EVO's ability to handle sustained random writes. This was interesting, as we limit our random write workload to an 8GB span, with the SSD only half full. This workload should fit within the SLC cache area of all three capacities tested. I'll investigate this further once we have all capacities available to test.
Burst Random %Read Sweep
Sweeps all follow as they should given the performance noted above. Nothing out of line here.