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Building Elastix-2.3 High Availability Clusters with DRBD and Heartbeat

Disclaimer
Use the information in this document at your own risk. Use of the concepts, examples, and/or other content of this document are entirely at your own risk. All copyrights are owned by their owners, unless specifically noted otherwise. Use of a term in this document should not be regarded as affecting thevalidity of any trademark or service mark. You are strongly recommended to take a backup of your system before major installation and backups at regular intervals.

Credits
Special thanks to Telesoft Integrando Technologies whose earlier documentation on doing DRBD in Elastix was a great reference for this work; http://asterisk.aplitel.info/files/asteriskcluster.pdf Another special thanks to AmjadJabali for the Elastix 1.6.0 Clustering tutorial that this document is based on.
http://ftp.heanet.ie/disk1/sourceforge/e/el/elastix-easy/Documents/Elastix-Clustering.pdf

A final special thanks to the Escuela Politécnica del Ejercito (Sangolquí – Ecuador) for the help provided by their staff and faculty members in the Elastix Project Overview. If by any way you can contribute to polish this workfeel free to write to my e-mail and send me your documentation. Remember Open Source is based on community effort, so any recommendation to improve it is appreciated and valued.

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INDEX

Operational Overview…………………………………………………..….3 What Is DRBD………………………………………………….…....3 What Heartbeat does………………………………………….…....4 Equipment Overview……………………………………………………….4 DRBD Install andConfiguration…………………………………………..5 Heartbeat Configuration………………………………………….…….…10 Credits…………………………………………………………………......12 References……………………………………………………………......12

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Operational Overview
What is DRBD?

DRBD® refers to block devices designed as a building block to form high availability (HA) clusters. This is done by mirroring a whole block device via an assigned network. DRBD can be understood as network based raid-1.In the illustration above, the two orange boxes represent two servers that form an HA cluster. The boxes contain the usual components of a Linux™ kernel: file system, buffer cache, disk scheduler, disk drivers, TCP/IP stack and network interface card (NIC) driver. The black arrows illustrate the flow of data between these components. The orange arrows show the flow of data, as DRBD mirrors thedata of a highly available service from the active node of the HA cluster to the standby node of the HA cluster. In our implementation we will be creating a DRBD synchronized partition on /dev/sda3 called “replica”. This partition will contain only those directories and files we want synchronized between our primary and secondary server. Namely, the important Asterisk and Elastix related directoriesand files.

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The upper part of this picture shows a cluster where the left node is currently active, i.e., the service's IP address that the client machines are talking to is currently on the left node. The service, including its IP address, can be migrated to the other node at any time, either due to a failure of the active node or as an administrative action. The lower part of theillustration shows a degraded cluster. In HA speak the migration of a service is called failover, the reverse process is called failback and when the migration is triggered by an administrator it is called switchover. In our implementation we will utilize Heartbeat to monitor the state of two servers and during a failover mount our synchronized partition on the secondary server and start up thefollowing resources/applications; asterisk, mysql and http. During failover our floating IP address will move from the primary to the secondary server. This IP address should be used to register SIP and other VoIP endpoints.

Equipment Overview
This installation scenario assumes two servers, each with three Ethernet interfaces and a single SATA hard drive. You may have a different type of...