Comparing strings

Hello

I can't get this right. What I have is a script to backup VM guests. The command is called with an argument, for example:

/usr/local/bin/vm-backup.sh FOO

Some of the VMs have two disks and I want to back them both up. Two of the VMs have vert large data partitions that are backed up separately and I want to exclude them. 

If I do this: 

if [ "$1" != "FOO" ];
 then
       echo "I can backup the 2nd volume";
else
        exit;
fi

It works. But if I add an "or" condition as follows:

if [ "$1" != "FOO" ]   ||  [ "$1" != "BAR" ] ;
 then
       echo "I can backup the 2nd volume";
else
        exit;
fi

It fails. I have tried this a number of different ways and I can't get it. Any guidance is appreciated. Thanks.