Triple-Level Cell TLC NAND based SSDs perform usually quite well, but when you copy a large amount of data to the drive without and idle time you’ll often find a large drop in write speed. TLC NAND is great in applications where write operations are limited , but is usually not recommended for critical systems that have heavy write operations as they have lower endurance ratings than SLC or MLC NAND and of course sustained write performance isn’t stellar. In recent years drive manufactures have been figured out that by using SLC or TLC treated as SLC as a cache they can keep the drives overall write performance high as long as the amount of data being written to the drive fits in the cache. If you overflow the cache, you are then writing directly to the TLC NAND and the write performance will drop down to that level. It should be noted that the SLC cache will clear once the drive idles, so this only impacts long writes that are many GB in size. This might not be a typical workload scenario for this ultra-value or mainstream drives, but still something worth pointing out!
When you average the test results over the 45 second period that we are focusing on these are the average speeds that you come up with:
The ADATA SP550 series drives clearly do not have good sustained write performance! Most TLC NAND based drives have serious issues with sustained writes, but as you can see there are some TLC drives on the market that do much better with sustained writes. One of the interesting things that we learned by doing this test is that there is a write performance difference between the 240GB and 480GB models with regards to sustained writes once they begin being written directly to the TLC NAND.
Let’s take a look at some common benchmarks!