SARK High Availability

The SARK Dual Server HA solution is the perfect IP telephony solution for mission critical businesses requiring high levels of resilience and backup.

Telephony is one of the most critical parts of any businesses today. With the ever growing increase in IP telephony it has become evidentially important for businesses to make sure the connectivity for SIP trunks are functional at all times and should they fail there is the minimum disruption and down time.

The SARK HA package provides the complete solution to ensure customers get the best level of resilience for their business communications. SARK HA is referred to as a cluster solution which delivers fully automatic hardware fail over.

How it works:

High availability is achieved by running two PBX instances in parallel. One of the PBX servers acts as Primary node and the other as Secondary node. Both systems communicate via a special "Heartbeat" method across a serial cable link and share a virtual IP address. The virtual IP address is used by IP phones and SIP trunks for connection with the SARK HA cluster. If the primary server goes down the secondary server waits for 20 seconds before taking over and business calls continue as normal.

Switching ISDN Lines between SARK HA Pair:

From above we have dealt with how the SARK HA provides backup for IP telephony but what about any ISDN lines that are connected to the system. There are quiet a few ways to handle fail over of ISDN lines on a HA system. The easiest and most commonly used scenario is to use a SIP to ISDN Gateway (we recommend the Sangoma Vega Range). The Sangoma range of gateways connect to SARK over the IP network and ISDN on the other side. The failing of primary server will not effect calls from ISDN or PSTN as the standby system will be using the same shared virtual IP address used by primary server for connection with Vega gateway.

Adding a Vega gateway adds some extra complications as it is yet another single point of failure but this may be a reasonable compromise for some customers.

ISDN failover using Vega Gateway in HA System

Diagram shows: ISDN failover using Vega gateway in HA System

ISDN 30 Switching between HA Pair:

Another robust way of handing fail-over of the ISDN lines is by using an optional in-built ISDN card fitted within the SARK PBX together with a Rhino fail-over card. In the event of failure of the primary node it immediately sends a signal to the Rhino card to switch the ISDN calls to the secondary node.

ISDN failover using Rhino failover cards in HA System

Diagram shows: ISDN failover using Rhino failover cards in HA System

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