Memory and Storage Speeds on Optane DIMMS
At Flash Memory Summit, I showed why 3D XPoint was advertised as 1000x faster but ended up only 7x Faster. It has to do with the fact that individual IOPS, latency, sequential read speed may or may not be limiting factor. Actual impact is always less. The best example is based on HDD to SSD comparisons from the many benchmarking sites. SSDs are technically 500x faster than HDDs… but in most applications your apps run <2x faster....
Next week, Intel will publicly update us with info on Cascade Lake and Optane DIMMS. The above mentioned challenge will be a bit of a two edged sword for Optane DIMMS.
- Optane DIMMS used as persistent memory will be 50 times faster than NVMe SSDs based on latency and bus speeds. This sounds great but we will find most applications do not see that level of benefit. The UCSD team did a great study on this. Whether it is worth the price and time to optimize is up to you and your applications
- On the other hand, Optane DIMMs used in main memory with a DRAM cache (“memory mode”) will provide tons of main memory that is theoretically 7-10x slower that DRAM RDIMMs based on latency… but actual speed difference will be less than that and if the data is “cache friendly”, maybe 90% of applications will see no measurable difference in actual use. Lots of memory, lower cost than DRAM, same measurable performance in most cases. Whether it is worth the price and time to optimize is up to you and your applications
So we will find that in actual use, Optane DIMMS are not 50x faster than SSDs… but they are not 10x slower than DRAM either. We will see what performance actual customers see in months to come