We Replaced an SSD with Storage Class Memory; Here is What We Learned

Intel Optane Persistent Memory (SCM) was introduced as a storage class memory product in April 2019. It is designed to be both persistent like an SSD and fast like DRAM, sitting on the memory bus. Experiments were conducted comparing SCM with SSDs using MongoDB's WiredTiger storage engine. The results showed that while SCM has a higher bandwidth than a technology-equivalent SSD, the advantage is within an order of magnitude and effective DRAM caching hides this difference. However, SCM can shine in latency-sensitive operations such as logging where it offers significantly lower read latencies compared to SSDs.