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Chapter 1 System Overview and Requirements
© 2017 Harmonic Inc. All rights reserved.
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Harmonic MediaGrid Release 4.1
About Clusters, Volumes and Groups
About Clusters, Volumes and Groups
When setting up a Harmonic MediaGrid 4000 or 3000 system, generally, there will be one
cluster, one volume, and one group, all of which are generated automatically by the configuration
assistant.
Keep in mind the meaning of these concepts:
A
Cluster
includes a Volume and its associated ContentDirectors, ContentServers and
ContentStores within a Harmonic MediaGrid.
A
Volume
includes the file system, one Group, and its associated ContentServers and
ContentStores in a Harmonic MediaGrid.
A
Group
is a collection of one or more ContentServers and ContentStores in a Harmonic
MediaGrid.
About a Harmonic MediaGrid Stretch Cluster
Harmonic MediaGrid supports using replication on systems with the ContentServer 3000 Series.
This feature provides an additional level of data protection by allowing you to set up a Harmonic
MediaGrid system across two different sites and replicate data across sites. This configuration is
known as a “stretch cluster.” In the event of a site failure, replication ensures that the data will be
available at the second site.
Because of the added redundancy in a stretch cluster, note that storage capacity will be reduced.
Make sure to work with your Harmonic representative to size your system appropriately. Also
note that although this configuration results in faster read operations, write operations are slowed.
System Requirements
To configure a stretch cluster, you must have a
minimum
of six nodes in the cluster. This
means each of the two sites in the cluster must include at least one ContentServer with two
ContentStores connected to it.
The two sites in a stretch cluster must be no more than 20 kilometers apart.
Each ContentDirector in your system must have a fiber optic network card installed. For
assistance, contact your Harmonic representative.
Systems must be configured with two groups, one for each site.
Each group in the cluster must have the same amount of storage with exactly the same
combination of ContentServers and ContentStores.
The replication factor for the cluster must be set to 2.
Sample Diagram
Figure 1–1
shows a sample stretch cluster.
NOTE:
The dark blue lines and gray lines represent different connections on the same Public VLAN.
NOTE:
For cross-site connections, you must use fiber optic cable attached to a fiber optic card installed
on the ContentDirector.