Disaster Tolerance and Recovery in a Serviceguard Cluster

Understanding Types of Disaster Tolerant Clusters

 

architecture are followed. Extended distance clusters were formerly

 

known as campus clusters, but that term is not always appropriate

 

because the supported distances have increased beyond the typical size

 

of a single corporate campus. The maximum distance between nodes in

 

an extended distance cluster is set by the limits of the data replication

 

technology and networking limits. An extended distance cluster is shown

 

in Figure 1-3.

 

 

NOTE

There are no rules or recommendations on how far the third location

 

must be from the two main data centers. The third location can be as

 

close as the room next door with its own power source or can be as far as

 

in a site across town. The distance among all three locations dictates the

 

level of disaster tolerance an extended distance cluster can provide.

 

In an extended distance cluster, for data replication, the Multiple Disk

 

 

(MD) driver is used. Using the MD kernel driver, you can configure RAID

 

1 (mirroring) in your cluster. In a dual data center setup, to configure

 

RAID 1, one LUN from a storage device in data center 1 is coupled with a

 

LUN from a storage device in data center 2. As a result, the data that is

 

written to this MD device is simultaneously written to both devices. A

 

package that is running on one node in one data center has access data

 

from both storage devices.

 

The two recommended configurations for the extended distance cluster

 

are both described below.

Chapter 1

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