blk_update_request: I/O error, dev fd0, sector 0

It seems that kernel erroneously detected some device as floppy or just created a non existent reference because your machine does not have real floppy drive. So these blk_update_request for fd0 are completely unrelated to your hard drives. Many disk managing programs such as fdisk like to enumerate all available block devices, and definitely fdisk did hit floppy module and these messages started to appear in your dmesg.

Since your machine does not have floppy drive, it is safe and encouraged to remove and blacklist floppy kernel module so it will not bother you in future:

sudo rmmod floppy
echo "blacklist floppy" | sudo tee /etc/modprobe.d/blacklist-floppy.conf

then add /etc/modprobe.d/blacklist-floppy.conf to /etc/mkinitcpio.conf FILES variable and do mkinitcpio -p linux so initramfs will not load it too.

So after next reboot it will not appear and mess your steady configuration.

Use the below command and it will fix the problem for sure:

# sudo rmmod floppy
# echo "blacklist floppy" | sudo tee /etc/modprobe.d/blacklist-floppy.conf
# update-initramfs -u -k all

Reboot...