xNVMe in SPDK (bdev_xnvme)#
The xNVMe bdev module issues I/O to the underlying NVMe devices through various I/O mechanisms such as libaio, io_uring, Asynchronous IOCTL using io_uring passthrough, POSIX aio, emulated aio etc.
The user needs to configure SPDK to include xNVMe support:
configure --with-xnvme
To create a xNVMe bdev with given filename, bdev name and I/O mechanism use the bdev_xnvme_create RPC.
rpc.py bdev_xnvme_create /dev/ng0n1 bdev_ng0n1 io_uring_cmd
The most important I/O mechanisms are:
“libaio”
“io_uring”
“io_uring_cmd” (requires linux kernel v5.19 or newer)
To remove a xnvme bdev use the bdev_xnvme_delete RPC.
rpc.py bdev_xnvme_delete bdev_ng0n1
For more information on SPDK bdev refer to SPDK: https://spdk.io/doc/bdev.html
Feature comparison#
SPDK: |
SPDK: |
xNVMe |
|
|---|---|---|---|
Flush |
✓ |
||
Write |
✓ |
✓ |
✓ |
Read |
✓ |
✓ |
✓ |
Write Uncorrectable |
✓ |
||
Compare |
✓ |
✓ |
|
Write Zeroes |
✓ |
✓ |
✓ |
Dataset Management |
✓ (unmap) |
✓ |
|
Verify |
✓ |
||
Copy |
✓ |
✓ (scopy) |
|
Compare and Write (fused command) |
✓ |
||
Reset |
✓ |
✓ |
|
Zone Append |
✓ |
✓ |
|
Zone Management Receive |
✓ (Get Zone Info) |
✓ |
|
Zone Management Send |
✓ (Zone Management) |
✓ |
|
NVMe (passthru) |
✓ |
✓ |
|
Abort |
✓ |
||
Hot Remove |
✓ (hotplug) |
||
Protection Information |
✓ |
✓ |