 High-Availability Cluster with Linux-HA Matt Varnell Cameron Adkins Jeremy Landes

Computer Cluster  A group of linked computers, working together as a single computer.  Computers connected to each other through fast local area networks.  Used to improve performance and reliability over that of a single computer.

High-Availability Cluster  Implemented to improve the availability of services that clusters provide.  Redundant nodes are used to provide replacement services when system components fail.  Redundant nodes means same OS, data, system clocks, etc.  Most commonly consist of two nodes (minimum requirements)  This system eliminates single points of failure from bringing down the entire cluster.

Running a single server setup after crashing  This leads to any tasks needing to go through the server or use software from it to be put on hold until the problem is solved.  A system administrator would have to fix the issue before the server could be used again.

Solution: A High-availability Cluster setup.  If the main node crashes, there is a secondary node available with redundant data that will immediately start running in the case of a primary crash.  No outside assistance needed to bring the system back up in case of a crash.

Node Configuration  Active/Active (traffic is load balanced across available nodes)  Active/Passive (all nodes are fully redundant – hardware heavy setup)  N+1 (single extra node brought online in the case of a node failure)  Also N+M, N-to-1, N-to-N (variations on the N+1 model depending on system setup)

Heartbeat Architecture  Two systems share a heartbeat over a private closed loop.  Consists of a sequence of simple messages using checksums to ensure normal activity.  If heartbeat is lost, the secondary node acquires resources from the primary node.  Uses redundant physical loops to monitor heartbeat between the systems:  Serial ports: Two node monitoring using a serial cable plugged into both devices.  Ethernet ports: Uses a crossover cable and private IP network between both hosts.

Linux-HA  The Linux HA working group (Linux.org) has developed a heartbeat architecture that supports a wide array of HA internode communications mechanisms and media.

Linux-HA  Works to provide a high availability clustering solution for Linux, Solaris and Mac OS X.  Main software product of this project is Heartbeat, a cluster management program for HA clustering.  Features:  No fixed maximum number of nodes (from very small to large clusters)  Resource monitoring (automatic resource allocation)  Fencing mechanisms (failed node removal)

Work Citied   proxy.radford.edu/?genre=article&isbn=&issn= &title=Electronic+E ngineering+Times+% %29&volume=&issue=1112&date= &atitle=Building+Linux+high- availability+systems.&aulast=Ramsey%2c+Brian&spage=92&pages=92- 95&sid=EBSCO:Academic+Search+Complete&pid=   basics-CSO.html