Question AT Bench : Samsung 970 Evo plus 2TB vs 1TB

[coolrock2008]

I was looking for the benchmarks comparing SK hynix Gold P31 to Samsung 970 line when i noticed this oddity.

The 970 Evo plus 2TB has a considerable lower latency in ATSB Heavy workloads than the 1 TB model. In the light and Destroyer workloads, they are comparable. Wonder why this difference. Should we chalk it down to an issue with the test, randomness or there something else?

 

[Billy Tallis]

The 2TB 970 EVO Plus has a larger SLC cache, by about 50%. The ATSB Heavy test has enough writes to theoretically fill the cache on either model if all the writes were issued to the drive as fast as possible. But since the test isn't quite that intense, the drives can spend some time flushing the cache. I suspect that in practice, the 2TB model does not experience the SLC cache overflowing during the Heavy test, but the 1TB model does. Both drives run out of SLC cache during The Destroyer, and neither runs out of cache during the Light test.

The 1TB 980 PRO has a much larger SLC cache than the 1TB 970 EVO Plus, and its ATSB Heavy performance is a lot closer to the 2TB 970 EVO Plus.

 

[coolrock2008]

The 2TB 970 EVO Plus has a larger SLC cache, by about 50%. The ATSB Heavy test has enough writes to theoretically fill the cache on either model if all the writes were issued to the drive as fast as possible. But since the test isn't quite that intense, the drives can spend some time flushing the cache. I suspect that in practice, the 2TB model does not experience the SLC cache overflowing during the Heavy test, but the 1TB model does. Both drives run out of SLC cache during The Destroyer, and neither runs out of cache during the Light test.

The 1TB 980 PRO has a much larger SLC cache than the 1TB 970 EVO Plus, and its ATSB Heavy performance is a lot closer to the 2TB 970 EVO Plus.

Thank you for your reply. The SLC cache size indeed helps explain the difference.