Red Hat CLUSTER SUITE FOR ENTERPRISE LINUX 5.1 Instrukcja Użytkownika Pobierz pdf (Strona 30)

Introduction to Linux Clustering

load balance between your geographically separated servers – this is good for

services such as HTTP or read-only database requests.

8.4.1 TWO NODE DISTRIBUTED CLUSTER

As discussed above, a two-node distributed cluster is able to use DRBD data replication

which solves the major challenge of mirroring the data.

This two-node setup is an ideal solution for organisations which want the redundancy of an

off-site mirror suitable for providing both redundancy and load-balancing. It is also suitable

for organisations which have two offices and wants identical servers at both locations.

This example assumes the following environment:

● Two geographically separated servers, identical hardware.

● Network between both servers controlled by an outside party (therefore floating IP

addresses are not possible)

● No plans to scale beyond two nodes.

Requirements:

● Have a server at both locations.

● Both servers need to offer file sharing to the local networks at each office with

Samba.

● Mail, DB and HTTP services required to be HA.

Solution:

● Servers setup with DRBD in primary/primary setup (both servers can read/write).

● GFS filesystem to allow both nodes simultaneous access to the data.

● Use ping to a remote server to determine tie-breaker third vote. (Quorum heuristics)

● Floating DNS names for services.

● Cluster suite capable of migrating individual services.

MAIL, DB and HTTP services will only run on one server at any time (otherwise

interesting lock file issues would occur).

In the event of either server suffering a failure, the services will be relocated to the

alternate server and the DNS records will be adjusted to redirect traffic.

Samba runs on both servers providing access for the local network. In the event of a

server failure, the DNS name for the local network server will be changed to be the

alternate server.

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Red Hat CLUSTER SUITE FOR ENTERPRISE LINUX 5.1 Instrukcja Użytkownika Strona 30