Assuming you want to rename the md device to be `data`, you can do it by performing the following steps:
`sudo mdadm --stop /dev/md127`
`sudo mdadm --assemble /dev/md/data --name=data --update=name /dev/xdvi1 /dev/xdvj1`
`sudo mdadm --detail --scan`
- You will get something like this,
`ARRAY /dev/md127 metadata=1.2 name=tmp-mdadm:127 UUID=af8d2901:f37333e6:d8490a00:2855a00e`
- If you want to name the md device as "data", you put
`ARRAY /dev/md/data metadata=1.2 name=tmp-mdadm:data UUID=af8d2901:f37333e6:d8490a00:2855a00e` into the file `/etc/mdadm/mdadm.conf`.
`sudo reboot`
Just to add to haimg's excellent answer. It may happen that even with a mdadm.conf, the system (at least for Ubuntu) may still auto-assemble the arrays prior to reading mdadm.conf. So when it finds it it just ignores the arrays that have just been assembled anyway.
To account for that, run sudo update-initramfs -u to regenerate the proper initrd.
References: