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Results: Write Saturation

JMicron Returns: The JMF667H Controller On Four Reference SSDs
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Random Performance Over Time

My saturation test consists of writing to each drive for 12 hours using 4 KB blocks with 32 outstanding commands. But first I secure erase each drive. Then, I apply the write load, illustrating average IOPS for each minute (except for the last 20 minutes, where I zoom in and show you one-second average increments).

Example: Intel's SSD 730Example: Intel's SSD 730

The above chart comes from The SSD 730 Series Review: Intel Is Back With Its Own Controller; consider it a reference of sorts. The 100% write (in pink), 50% write (in green), and 30% write (in blue) workloads are tightly grouped. There aren't any disturbing variations. And note the order of the bands: a 100% write generally results in the lowest performance, and as we add reads (as a percentage), we get progressively faster.

Now, this is from a production JMF667H-based drive, Transcend's 256 GB SSD340 with L85A flash, using older 263 series firmware. In other words, it's identical to the 256 GB L85A-based reference drive, except that JMicron's implementation employs newer 417 firmware.

Look at the order of those bands. The 50% write trace falls below the 100% write workload, and that's not orthodox. When I first saw this, before getting my hands on the reference platform with its newer firmware, I assumed something was wrong. But then, take a look at this:

This is JMicron's reference SSD with the 417 firmware. It's actually less consistent, but that's partly because performance was so low before. That 50% write band shows up above 100%, but below 30%, where it should be. Clearly, the newer firmware's garbage collection and background processes are far more optimized.

What happens when JMicron swaps in A19 flash? Does that make an appreciable difference?

This is the 128 GB reference drive with 64 Gb A19. It's clean and pretty. The bands are narrow and distinct, with few outliers. The 100% write separates into two layers, but is still orderly-looking. Actually, I'm amazed at how much the saturation test changes after swapping around some flash. I know Plextor's drives do well in this metric too, and it's possible that the good behavior is related to reliance on Toshiba's Toggle-mode interface. JMicron looks to have its act together here.

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