Despite NVMe being the future, SAS is still widely deployed in enterprise storage arrays and in enterprise servers. While SATA ran out of performance headroom as we discussed in our Kioxia CD6 PCIe Gen4 NVMe SSD review, SAS is able to continue scaling to higher bandwidth levels, the next being SAS4 which is a 24Gbps interface (SATA III is 6Gbps for reference.) For this next-generation storage interface, Samsung has a new SSD. Dubbed the Samsung PM1653, the company is announcing the drives before mass production later in 2021.
Samsung PM1653 24G SAS4 SSDs
The Samsung PM1653 is the company’s first 24G SAS SSD. It will be built using the company’s 6th generation V-NAND chips.
Samsung says capacities are expected to range from 800GB to 30.72TB. Random performance is supposed to hit around 800K IOPS and sequential read speeds of around 4.3GB/s. As one would expect with modern data center NVMe SSDs being significantly faster, this performance is being limited by the 24G SAS interface, not the NAND technology.
The major challenge in the industry is that 24G SAS (SAS4) drives will hit the market in the second half of 2021. We also need PCIe Gen4-based SAS4 controllers to be widely available and systems to be validated. It is likely we are going to see 24G SAS adoption around the time that PCIe Gen5 and CXL hit the market in 2022 which means that SAS SSDs will again seem more than a generation old. The new Samsung SSDs can hit 4.3GB/s in sequential reads, but its consumer M.2 SSD, the Samsung 980 Pro we reviewed in 2020 is hitting 50% or more read throughput than the future SAS drive launched in late 2021. Granted, they are very different drives, with different deployment scenarios and workload optimizations, but that is the challenge. 24G SAS is coming out with PCIe Gen4 out-pacing drives, and just as the PCIe Gen5 drives will be close to hitting the market. From a timing perspective, delaying storage purchases will likely see 3x the performance per device by waiting for next-gen PCIe Gen5 NVMe SSDs.
Still, there is a market for SAS, but it seems like the primary market is going to be in legacy systems that have not made the jump to newer PCIe infrastructure. We purchase SSDs for higher performance, and 24G SAS helps, but is notably falling behind NVMe storage technology.