Hardware used: CM6 and an NVME brand of fanxiang.
I used an NVME brand to connect to the M2 port of the CM6.Then use the command to query：
The memory size of the device and nvme can be queried by lspci and lsblk.
pi@bananapicm6io:~$ lspci
0001:00:00.0 PCI bridge: Device 201f:0001 (rev 01)
0001:01:00.0 Non-Volatile memory controller: MAXIO Technology (Hangzhou) Ltd. NVMe SSD Controller MAP1202 (DRAM-less) (rev 01)
0002:00:00.0 PCI bridge: Device 201f:0001 (rev 01)
pi@bananapicm6io:~$ lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINTS
mmcblk2 179:0 0 14.6G 0 disk
├─mmcblk2p1 179:1 0 256K 0 part
├─mmcblk2p2 179:2 0 64K 0 part
├─mmcblk2p3 179:3 0 1M 0 part
├─mmcblk2p4 179:4 0 2M 0 part
├─mmcblk2p5 179:5 0 256M 0 part
└─mmcblk2p6 179:6 0 8G 0 part
mmcblk2boot0 179:8 0 4M 1 disk
mmcblk2boot1 179:16 0 4M 1 disk
mmcblk0 179:24 0 14.8G 0 disk
├─mmcblk0p1 179:25 0 256M 0 part /boot
└─mmcblk0p2 179:26 0 14.3G 0 part /var/log.hdd
/
nvme0n1 259:0 0 238.5G 0 disk
Read test：
pi@bananapicm6io:~$ sudo hdparm -Tt /dev/nvme0n1
/dev/nvme0n1:
Timing cached reads: 2930 MB in 2.00 seconds = 1465.61 MB/sec
Timing buffered disk reads: 1908 MB in 3.00 seconds = 635.72 MB/sec
Write test：
pi@bananapicm6io:~$ time dd if=/dev/zero bs=1024 count=1000 of=/dev/nvme0n1
1000+0 records in
1000+0 records out
1024000 bytes (1.0 MB, 1000 KiB) copied, 0.0262977 s, 38.9 MB/s
real 0m0.032s
user 0m0.001s
sys 0m0.018s