"PCIe-over-Cable” is also known as PCI-Express Bus Expander solution. The idea of “PCIe-over-Cable” is to extend the internal PCI-express bus outside the computer into another external enclosure, and then allows adding more PCI Express bus Devices(add-on cards) in the external enclosure, just as if they were added inside the computer which the PCIe bus is extended from.
While the concept of “PCIe-over-Cable” is good, there are some facts that must be pointed out, which are often omitted by “PCIe-over-Cable” vendors:
Fact #1: “PCIe-over-Cable” solution is not “host independent”. Whatever PCIe device(such as SAS RAID adapter or Fibre HBA, etc) installed in the external enclosure still needs to install software device driver in the computer, no difference from the SAS RAID adapter + E2128J JBOD solution.
Fact#2: For the “PCIe-over-Cable” solution with PCIe x 8 implementation, vendors often claim that the solution can provide up to 20Gbps total bandwidth. But those vendors also often forgot to tell you that, the actually bandwidth is also depending on the Quality-of-Service at the end point, which is the PCI-e device to be installed.
For example, installing a SAS RAID adapter in a PCIe-over-Cable external enclosure is not going to perform faster than installing it inside the computer and connected to E2120J, because, the SAS RAID adapter is the end-point/key factor here for the whole performance/bandwidth equation. If the SAS RAID adapter can only deliver 1000MB/sec, putting it on a 2000MB/sec bus would not make it run faster, also, it is no difference from putting it inside the computer on a PCIe x8 slot.
Fact#3: while the “PCIe-over-Cable” is a good concept, the actual result depends on each vendor’s own implementation, design quality, and manufacturing quality. Put the “quality” issue aside, just the “how it is implemented” alone plays a big part in end result of the solution.
The conclusion: at current stage, using a SAS/SATA RAID adapter in the “PCIe-over-Cable” solution (PCIe x8) is not better than using the same SAS/SATA RAID adapter + E2128J JBOD for performance, in some cases, due to actual implementation limitation, “PCIe-over-Cable” solution is less attractive.
Please also visit E2128J_vs_HDPro for comparison.
Disclaimer:
#1: the author has tried his best efforts to be as much accurate as possible based on publically available information at the time this paper is published. No private or confidential information is use. If there is any error and/or mistake contained in this paper, it is purely unintentional and accidental. The author is not responsible for the results due to future changes in hardware, firmware, software, components.
#2: If any one finds this paper contains inaccurate or un-true statements, please contact us, and we will correct it ASAP.