Difference between RHEL 6 and RHEL 7

RHEL 6

• Red Hat Enterprise Linux 6 initially released on 10 November 2010 with the release name Santiago and it is forked from Fedora 12
• The initial kernel version was 2.6.32-131 (6.1) and it can be updated to 6.10 - 2.6.32.754
• It's support will end in June 2024 as per the Extended Life-cycle Support 
• RHEL 6 supports both 32 and 64 bit architecture 
• The default file system is EXT4 but can be choose the other's as well and EXT4 supports 16TB partition size and XFS 100TB
• Kdump doesn't support large RAM size
• There are run levels 0-6,each have their own functionality 
• In service management it uses checkconfig commands to manage services
• Iptables are used in RHEL 6 as firewall configuration,routes traffic and security 
• At the startup processes the system V (init.d) scripts used to run the services and its demons 

RHEL 7

• Red Hat Enterprise Linux 7 released on 10 June 2014 with the release name Maipo and it is based on Fedora 19
• The RHEL 7.1 kernel version was 3.10.0-229 and latest update till now is 7.6 - 3.10.0.-957
•  RHEL 7 only support 64 bit architecture 
• The default file system is XFS but can be choose the other' as well and XFS supports 500TB partition size
• Kdump supports can be upto 3TB
• There are no run levels in RHEL 7 but it has targets to do the job of run levels
• Boot loader version changed to Grub 2 and default database is now MariaDB as in RHEL 6 it was MySQL
• In RHEL 7 service management it uses systemctl commands to manage services
• RHEL 7 switched to firewalld concept for firewall configuration and security policies
• At the startup processes the systemd is now used to run the parallel processes and its demons and this is the major change which can fast the loading services
• The service is handling better with systemctl as status argument with addition switches like -l give detailed logs of the running services