# ls -lah /dev | grep md
drwxr-xr-x  2 root root       100 May 24 18:36 md
lrwxrwxrwx  1 root root         4 May 24 18:36 md0 -> md/0
brw-r--r--  1 root root    9,   1 May 24 18:36 md1
lrwxrwxrwx  1 root root         4 May 24 18:36 md2 -> md/2

# mount /dev/md1
mount: mount point none does not exist

# swapon -a
swapon: /dev/md1: Invalid argument

# mkswap /dev/md1
mkswap: error: swap area needs to be at least 40kB
Usage: mkswap [-c] [-v0|-v1] [-pPAGESZ] [-L label] /dev/name [blocks]