sub build_disk_list {
    my $self = shift;
    my $disk_names = shift;

    my @letters = 'a' .. 'zz';
    my @disk_letters = @letters[ 0 .. $#{$disk_names} ];

    my $disk_it = each_array @{$disk_names}, @disk_letters;
    my @disk_list;
    while ( my ( $disk_name, $disk_letter ) = $disk_it->() ){
        push @disk_list, [$disk_name, "vd" . $disk_letter ];
    }
    return \@disk_list;
}