Results: 128 KB Sequential Read And Write
Fantastic sequential read and write performance is a trademark of modern SSDs. To measure it, we use incompressible data over a 16 GB LBA space, and then test at queue depths from one to 16. We're reporting these numbers in binary (where 1 KB equals 1024) instead of decimal numbers (where 1 KB is 1000 bytes). When necessary, we also limit the scale of the chart to enhance readability.
128 KB Sequential Read
There's not much difference between drives in this metric. Then again, I didn't expect any. Getting 538 MiB/s is about all we'll see from SATA 6Gb/s, and these could have been any three drives to pass through my lab lately; they're all hitting the interface's ceiling. On to the writes.
128 KB Sequential Write
The 128 GB 850 Pro is the only drive to register lower performance, as we knew would be the case. But hitting 460 MB/s is no joke. No other 128 GB drive I have comes close. Note that, first, I'm using 128 KB access sizes, and second, reporting in binary, not decimal. In decimal, that'd be 482 MB/s. Put another way, the 128 GB 850 Pro pushes 100 MB/s more than the 840 Pro at 128 GB.
Samsung's 256 and 1024 GB models are blazing fast, demonstrating throughput in excess of 510 MB/s (again, in binary). That's as fast as you're going to see from a SATA 6Gb/s-based SSD.
Here's a breakdown of the maximum observed 128 KB sequential read and write performance with Iometer:
Sorted by combined maximum read and write throughput, two 850 Pros establish beachheads just below the pair of PCIe-based SSDs. No drive with a SATA interface can claim to deliver more sequential performance. And again, dig through this chart and you'll find that no competing 128 GB-class offering touches the 850 Pro.