Comment 1 for bug 1756315

Can you try the following?

mdadm --create --verbose /dev/md0 -l0 -n2 --chunk 4096 /dev/nvme0n1 /dev/nvme1n1

The modern SSD (As available in the I2/I3 instance types) and the HDD (As found in D2) have a native sector size of 4096 Bytes, and that matches sector size for Linux LVM and pages.

I think you probably have a chunk size of 256, a write (or TRIM) of each 4K sector would be spread into 16 chunks, making each access of the SSD a partial native sector.