====== Introduction ====== LiteSpeed High Availability (HA) leverages the existing packages available and builds its own strength to it. On Freebsd platform, CARP (Common Address Redundancy Protocol) is used to have multiple hosts to share the same IP address (VIP). On Linux platform, Keealived is used to achieve the common IP address failover. ====== HA on FreeBSD ====== CARP ===== Requirements ------------------- To enable CARP support, the FreeBSD kernel must to be built with following option device carp Alternatively, the if_carp.ko module can be loaded at boot time. To do that, add the following to the /etc/load.conf if_carp_load="YES" CARP functionality may be tuned via sysctl OIDs: OID Description net.inet.carp.allow Accept incoming CARP packets. Enabled by default. net.inet.carp.preempt This option downs all of the CARP interfaces on the host when one of them goes down. Disabled by default CARP for Failover (HA) ------------------------------- Within a subnet (LAN), multiple host share the same IP (VIP) to achieve service availability. One of the CARP's serve as Master, the rest as Standby. This is achieved via LSWS HA Configurations Interface (Admin CP). Option of Master/Standby is available. Master answers the requests sent to the VIP. The Standby's do not respond to the requests. When Master goes down, one of the Standby's takes over (becomes Master). When the Master is recovered, by default, it will immediately take over the VIP. ====== HA on Linux ====== Keepalived ========= Requirements ------------------- Linux Kernel has IP Forwarding enabled keepalived will: • setup the IP addresses (i.e., no need to create the IP's with ifconfig, etc) • handle failover between load balancers (i.e., no need to run heartbeat to watch for failures, or write scripts to handle the failure) Keepalived for HA ------------------------- Within a subnet (LAN), multiple host share the same IP (VIP) to achieve service availability. One of the hosts serves as Master, the rest as Standby. This is achieved via LSWS HA Configurations Interface (Admin CP). Option of Master/Standby is available. Master answers the requests sent to the VIP. The Standby's do not respond to the requests. When Master goes down, one of the Standby's takes over (becomes Master). When the Master is recovered, by default, it will immediately take over the VIP.