Comment Re:40 NVME ? (Score 1) 17
Storage people keep pushing the way it was done with fiber channel attached controllers abstracting things to generic block devices. Shared sas, fcoe, iscsi/iser... Have seen so many tries at bringing the concept and being ignored in favor of things like clustered filesystems and object store.
Clustered FS and Objectstore are built on top of SAS, FCOE, iSCSI, NVMe-OF. You first have to solve the problem of packing thousands of storage devices within the signal integrity radius of the transport medium before you can start abstracting. For NVMe that radius is about 1.5 - 2 meters from the CPU socket. SAS about 5 meters. Not sure on FC, I presume a couple km.
Just like hardware raid controllers are nearly non existent in nvme world
Completely common. Like 70% of all servers sold include a RAID controller that can talk to NVMe devices. But there's a catch... They suck so badly, nobody buys the PCIe cables to connect the backplanes. The inside joke is the best way to slow down your NVMe drives is to attach them to a RAID controller. Most NVMe drives use 4 PCIe lanes. Broadcom's RAID chips let them have two lanes. Then the RAID controller connects to the CPU with 16 lanes. So the minute you exceed 8 drives (via a switched backplane), you have an intractable bottleneck.
The Broadcom 3xxx chip hit the wall first as it still did RAID partially on the controller CPU. The 4116 implemented RAID entirely in silicon, the 51xx chips took this further with a complete cache redesign, and actually ditches SAS/SATA entirely. It's NVMe only. But nobody has solved the PCIe lane bottleneck.