On Wed, Feb 19, 2020 at 11:28:46AM -0500, Tim Walker wrote: > Hi Ming- > > >Will NVMe HDD support multiple NS? > > At this point it doesn't seem like an NVMe HDD could benefit from > multiple namespaces. However, a multiple actuator HDD can present the > actuators as independent channels that are capable of independent > media access. It seems that we would want them on separate namespaces, > or sets. I'd like to discuss the pros and cons of each, and which > would be better for system integration. If NVM Sets are not implemented, the host is not aware of resource separatation for each namespace. If you implement NVM Sets, two namespaces in different sets tells the host that the device has a backend resource partition (logical or physical) such that processing commands for one namespace will not affect the processing capabilities of the other. Sets define "noisy neighbor" domains. Dual actuators sound like you have independent resources appropriate to report as NVM Sets, but that may depend on other implementation details. The NVMe specification does not go far enough, though, since IO queues are always a shared resource. The host may implement a different IO queue policy such that they're not shared (you'd need at least one IO queue per set), but we don't currently do that.
