Specify the mapping of block devices. Has effect only when Use ephemeral devices is NOT checked. Format:
        <device>=<block-device>[,<device>=<block-device>]*
    
Where block-device format is:
        [<snapshot-id>]:[<size>]:[<delete-on-termination>]:[<type>]:[<iops>]:[encrypted]
    
Examples:
        /dev/sdb=snap-7eb96d16
        /dev/sdc=snap-7eb96d16:80:false
        /dev/sdc=snap-7eb96d16:80:false:io1:100
        /dev/sdd=:120
        /dev/sdd=:120::::encrypted
        /dev/sdd=:120::::encrypted,/dev/sdc=:120