The cache recovered partially after a few minutes of idle time, but the performance was still in a degraded state. However, it will recover fairly predictably. The cache isn’t as fast to recover as the company’s Rocket NVMe 4.0, as QLC NAND flash takes a lot longer to program. With such fast write performance out of the gate, the Q4 surpasses most SSDs until the cache fills, but it is a bit disappointing if your workload exceeds it. The SLC cache absorbs 1TB of data before write performance degrades from an average rate of 3.6 GBps down to 200 MBps (once filled). Sabrent’s Rocket Q4 delivers consistent write performance both in and outside of its SLC cache. 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 have 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. Sustained Write Performance and Cache Recovery
When taxed with heavier workloads, the drive scored top marks in random write performance but only delivered a bit over 213,000 random write IOPS.
The Rocket Q4 responds very quickly during random workloads at low queue depths, scoring a third-place ranking at QD1. After bumping up the QD a bit, the Rocket Q4 peaked at roughly 5/3.6 GBps read/write. The Rocket Q4 offers up very competitive performance and even matches the Rocket NVMe 4.0 in sequential read performance. We tested Sabrent’s Rocket Q4 at a queue depth (QD) of 1, representing most day-to-day file access at various block sizes.
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