ora-15063 asm discovered an insufficient number of disks for diskgroup

Problem : ora-15063 asm discovered an insufficient number of disks for diskgroup

Solution : 
make sure you have the following lines in /etc/raw file
raw5:sdb5
raw6:sdb6

mkdir /dev/raw
cd /dev/raw
mknod raw5 c 162 5
mknod raw6 c 162 6
modprobe raw (this command creates the /dev/rawctl file)
raw /dev/raw/raw5 /dev/sdb5
raw /dev/raw/raw6 /dev/sdb

cd /dev/raw
chown oracle:oinstall raw5 raw6 rawctl
chmod 777 raw5 raw6 rawctl