U2大船做阵列的方案讨论

rx_78gp02a

NVMe大部分都是软阵列，阵列卡的性能已经不够看了。

rx_78gp02a

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.

rx_78gp02a

诛仙 发表于 2023-9-8 17:27
顺带询问一下，LSI-9400-16i，要搭配什么硬盘拓展卡才能拓展4个以上的U.2硬盘？ ...

搭配PLX背板，U.2就是PCIE，PCIE只能上PCIE交换芯片

rx_78gp02a

xywjlidi 发表于 2023-9-8 18:19
这种PLX背板有产品吗？似乎都是pic-e接口的HBA卡，没有硬盘笼的背板，也没有expander卡。 ...

dell和联想有NVME背板，这东西是配套机箱笼子用的，你光找背板和expander卡肯定是找不到的。

rx_78gp02a

xywjlidi 发表于 2023-9-8 18:42
这种带plx的nvme硬盘笼有型号吗？咱能单独买笼子呢？

感觉买了也用不了，我手上有dell和联想的HBA卡，芯片其实就是PEX9733 ，但是单独接盘是无法认盘的，感觉是要和背板通信才能正常连接（老外测试也确实如此），也就是DELL的背板需要配DELL的HBA卡才行，你用LSI9400这种通路货，大概率无法连接专属背板。另外一种说法是，DELL/联想的HBA卡会根据背板的型号不一样，选择性拆分成4个X4还是两个X8或者不拆分直接X16，这些都是专属配件，无法单一使用。