Backends#
Below is a list of backends and the system interfaces and libraries they encapsulate. These backends implement the Backend Interface within the xNVMe library, offering a unified interface through the xNVMe API. This enables you to switch between system interfaces, libraries, and drivers at runtime without altering your application logic.
While xNVMe abstracts away most differences, it’s still important to understand the specifics related to your platform, system interfaces, and supporting libraries. For each backend we will cover the following topics: System configuration, device identification, and backend instrumentation.
- System Configuration
Some backends or I/O interfaces require you to configure your system in a certain way to use them. Examples include using a specific OS kernel or running a script to attach or detach devices.
- Device Identification
The schema for identifying devices differ across platforms and interfaces. Varying from file device handles, e.g.
/dev/nvme0n1, to PCI device handles, e.g.0000:02:00.0, and NVMe/TCP endpoints, e.g.172.10.10.10:4420.- Backend Instrumentation
On a given platform multiple interface may be available. At runtime, the xNVMe library makes a decision on which interface to use. You can overrule this decision, however, to do so, you need to know what the available options are, what they are named, and what they offer.
The valid combinations of interfaces and backends are listed below:
io_uring |
yes |
no |
no |
no |
no |
no |
io_uring passthru |
yes |
no |
no |
no |
no |
no |
libaio |
yes |
no |
no |
no |
no |
no |
kqueue |
no |
yes |
no |
no |
no |
no |
POSIX aio |
yes |
yes |
no |
yes |
no |
no |
NVMe Driver (vfio-pci) |
no |
no |
no |
no |
yes |
yes |
NVMe Driver (uio-generic) |
no |
no |
no |
no |
yes |
no |
I/O Control Ports |
no |
no |
yes |
no |
no |
no |
I/O Ring |
no |
no |
yes |
no |
no |
no |
emu |
yes |
yes |
yes |
yes |
yes |
yes |
thrpool |
yes |
yes |
yes |
yes |
yes |
yes |
nil |
yes |
yes |
yes |
yes |
yes |
yes |
psync |
yes |
yes |
yes |
yes |
no |
no |
Block-Layer ioctl() |
yes |
no |
yes |
no |
no |
no |
NVMe Driver ioctl() |
yes |
yes |
yes |
no |
no |
no |
NVMe Driver (vfio-pci) |
no |
no |
no |
no |
yes |
yes |
NVMe Driver (uio-generic) |
no |
no |
no |
no |
yes |
no |
libc |
yes |
yes |
yes |
yes |
yes |
yes |
hugepages |
yes |
no |
no |
no |
no |
no |