![]() As soon as their SLC cache runs out, the Crucial 1TB has the last laugh as it shows best sustained throughput, beating all cheaper drives, but the Kingston A400 comes close. It's funny to me that some cheap SSDs initially perform way better than the more expensive Crucial 1TB SSD 5. The raw Fio benchmark data can be found here (.tgz). Each drive has been benchmarked in full, but the data is truncated to the first 400 seconds for readability (performance didn't change). The chart below shows write bandwith over time for all tested SSDs. The benchmark is performed on the 'raw' device, no filesystem is used. Next, I performed a sequential write benchmark of the entire SSD with a block size of 1 megabyte and a queue depth of 32. Benchmark methodīefore I started benchmarking I submitted a trim command to clear each drive. To be frank, I'm not sure how much a lack of DRAM impacts our benchmarks. This can also impact (sustained) write performance. Cheap SSDs don't use DRAM cache chips to reduce cost, thus they have to update their data mapping tables in flash memory, which is slower. In addition, the DRAM can also be used to cache writes, improving performance. Keeping track of this mapping between logical and physical 'locations' can be sped up with a DRAM cache (chip) as DRAM tend to be faster than flash memory. DRAM cacheĪs flash memory has a limited lifespan and can only take a limited number of writes, a wear-leveling mechanism is used to distribute writes over all cells evenly, regardless of where data is written logically. While this trick with SLC memory works well for brief, intermittent write loads, sustained write loads will fill up the SLC cache and cause a significant drop in performance as the SSD is forced to write data into slower TLC memory. However, this process is limited by the speed of the 'slower' TLC flash memory and can take a while to complete. When the SSD is idle, data is moved from the SLC cache to the TLC flash memory in the background. ![]() This SLC memory then acts as a fast write cache 4. One technique to temporarily boost SSD performance is to use a (small) portion of (in our case) TLC flash memory as if it was SLC memory. All 'cheap' SSDs I benchmark use 3D v-nand 3 TLC flash memory. This is even more so for triple-level cell (TLC) and quad-level cell (QLC) flash memory. To reduce cost, multi-level cell (MLC) flash was invented, which can hold two bits instead of one, at the cost of speed and longevity 2. Unfortunately, it's also the most expensive. SSDs originally used single-level cell (SLC) flash memory, which can hold a single bit and is the fastest and most reliable flash memory available. ![]() ![]() Feel free to skip to the actual benchmarks if you're already familiar with them. To understand the benchmark results a bit better, we discuss some SSD concepts in this section. I've also added a Crucial MX500 1TB (CT1000MX500SSD1) SATA 1 SSD - which I already owned - to the benchmarks to see how well those small-capacity SSDs stack up to a cheap SSD with a much larger capacity. I didn't have the budget to buy a bunch of 1TB of 2TB SSD, so these ultra-cheap, low capacity SSDs are a bit of a stand-in. To demonstrate this concept, I bought a bunch of the cheapest SATA SSDs I could find - as listed below - and benchmarked them with Fio. However, at such low price points, there is a catch.Īlthough cheap SSDs do perform fine regarding reads, sustained write performance can be really atrocious. It's now possible to buy a 1TB solid-state drive for less than €60. The price of Solid-state drives (SSDs) has dropped significantly over the last few years. ![]()
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