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A Closer Look
The Longsys S500 uses an industry standard 2.5-inch form factor case with a 7mm z-height for compatibility with newer notebooks that require a low-profile chassis.
The PCB you find inside is very small; it doesn't even take up half of the available space inside the case. We started noticing this trend several years ago. It allows manufacturers to minimize production costs to stay competitive as SSDs become commoditized.
The final version of the SM2256 picked up the letter K at the end. We reached out to Silicon Motion for an explanation and were told that the K simply indicates a standard SM2256. This is a four-channel controller designed for mainstream users, so it is very power-efficient.
Longsys taps SK Hynix for its DDR3 buffer. The company also packages flash that it purchases from Micron, Toshiba and Samsung by the wafer. Again, the S500 we're testing today uses Toshiba's A19 TLC (19nm) NAND, with four packages on the PCB.
Data Type Comparison & SLC Cache
Silicon Motion controllers don't penalize high-entropy data with slow write speeds. Of course, it's important to buy the right SSD for your workload. You won't run into issues with this architecture if you specifically write a lot compressed data (multimedia, for example) like you would on some other drives. But that doesn't mean this SSD is your best choice for data-intensive tasks.
In fact, you'll run into performance issues when it comes time to write large files or lots of small ones to Longsys' S500. In the test above, we transferred 64KB blocks sequentially to see how long it'd take for write performance to drop to native TLC levels. Sixty-four kilobyte blocks allow us to see the drop-off better. Using 128KB blocks would nudge that boundary farther to the left, where it'd be hardly visible.
The two important take-aways from the graph are, first, that the SLC layer is quite small and, second, that the TLC's native 64KB sequential write performance is just under 90 MB/s. Small writes should be absorbed by the emulated SLC layer, but transfers of any substantial size will cut performance to half of what you can get from a modern mechanical disk.
