We also monitor cache recovery via multiple idle rounds. We use iometer to hammer the SSD with sequential writes for 15 minutes to measure both the size of the write cache and performance after the cache is saturated. Sustained write speeds can suffer tremendously once the workload spills outside of the cache and into the 'native' TLC or QLC flash. Most SSDs implement a write cache, a fast area of (usually) pseudo-SLC programmed flash that absorbs incoming data. Official write specifications are only part of the performance picture. Write speed and temperature are two important and inter-related metrics for external devices. Sustained Write Performance, Cache Recovery, and Temperature It's a responsive SSD with strong low-queue depth random read and write performance, which is important because this workload models normal light usage. With the X8's random 4K QD (queue depth) 1 read speeds being at least one-third faster than the competition, it's no wonder the X8 performs so well when we hit it with the easier workloads. It delivers very responsive performance under random workloads, too. Crucial's X8 hangs in there with the best during our sequential tests. The P5 is an excellent mid-range SSD that can run with the big drives in everyday performance, and even in all but the most demanding long transfers.