4 server redundant solution

• Servers 1 and 2 (S1 and S2) are identical. They server as gateways with Asterisk + MOR installed.
• Both of them have two network interfaces - one for http://en.wikipedia.org/wiki/Virtual_IP_address which is visible from outside, and one for local IP for interconnection heartbeat monitoring
• LinuxHA heartbeat monitors servers, e.g.
  • When S1 fails - S2 sees that and after 10s (default) will take main IP, e.g. will start to serve calls, it is done automatically
  • When S1 is back up - S2 returns main IP to S1 and system starts to function in normal work flow (done automatically).

• Servers 3 and 4 (S3 and S4) are identical. They server as MySQL DB.
• Both of them have two network interfaces - one for Main DB IP which is visible for Asterisk servers S1 and S2, and one for local IP for interconnection heartbeat monitoring
• LinuxHA heartbeat monitors servers, e.g.
  • When S3 fails - S4 sees that and after 10s (default) will take main IP, it is done automatically
  • When S3 is back up - S4 returns main IP to S3 and system starts to function in normal work flow (done automatically).
  • S1 connects to S3 over Main DB IP
  • S2 always interacts with S4 to take away load from main DB server (S3)
• DBs on S3 and S4 are synchronized over MySQL Replication

More info:

• 2 server redundant solution
• Linux Heartbeat