4 server redundant solution

Network setup

• Best scenario when all 4 servers are on the same LAN (subnet).
• Other possible solutions: Server 1 and 2 are on one LAN, Server 3 and 4 are on a different LAN (subnet). A VPN for better security from

servers 1 and 2 to servers 3 and 4 can be made.

• If all 4 servers are on different LANs (subnets), then between servers, VPNs have to be configured. Drawback - such a setup

becomes too complicated for management.

• If servers are in different countries (continents), it might cause latency problems, which has a negative influence on the speed of retrieving/inserting data to the DB (loading statistics, trying to retrieve some data, searching for a sound file, etc., will take longer than usual).
  

Workflow

• Servers 1 and 2 (S1 and S2) are identical. They serve as gateways with Asterisk + MOR installed.
• Both of them have two network interfaces - one for Virtual IP 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 Virtual IP, e.g., will start to serve calls, it is done automatically
  • When S1 is back up, S2 returns the virtual IP to S1, and the system starts to function in normal workflow (done automatically).

• Servers 3 and 4 (S3 and S4) are identical. They serve as a MySQL DB.
• Both of them have two network interfaces - one for Virtual DB IP (Virtual IP No. 2), 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), it will take the Virtual IP; it is done automatically
  • When S3 is back up, S4 returns the Virtual IP to S3, and the system starts to function in normal workflow (done automatically).
  • S1 connects to S3 over Virtual DB IP
• DBs on S3 and S4 are synchronized over MySQL Replication

More info:

• 2 Server Redundant Solution
• Linux Heartbeat