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For NVMe currently there’s limited availability of HW RAID options. Out of the 3 major HW RAID manufacturers, only one has come up with NVMe RAID implementation. While it has some of the familiar useful features of SAS RAID cards, it largely struggles with the performance of several NVMe drives and has a potential for being a bottleneck.
Problem points in HW RAID implementation for NVMe
ASIC IOPS capability. Even the newest RAID chips have a cap on the amount of IOPS they can process. With modern PCIe Gen.4 NVMe SSDs pushing above 1M IOPs per drive, even 3-4 drives can saturate a RAID adapter.
PCIe bandwidth bottleneck. With RAID adapter sitting on the PCIe bus between the drives and the CPU, the system performance is limited to the bandwidth of the single PCIe slot.
Latency. One of the key factors of the success of NVMe is low latency. This comes from the fact that the drives attach directly to the PCIe bus without any intermediate devices between the SSDs and the CPU. This helps ensure the lowest possible latency. Extra hardware between the drives and the CPU adds latency that negates one of the key advantages of NVMe.
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发表于 2023-9-8 17:05
