Specifications

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Cisco TV CDS 2.5 ISA Software Configuration Guide
OL-24788-01
Chapter 1 Product Overview
Content Delivery System Architecture
Vault Group Redundancy
In addition to the Vault server redundancy, the Cisco TV CDS offers redundancy for Vault Groups. When
the CDS is configured with Vault Group redundancy and at least two Vault Groups are configured, the
system handles the loss of an entire Vault Group without impacting the subscriber experience. Content
is mirrored among as many as four Vault Groups (one Vault Group ingests the content and up to three
Vault Groups mirror the content), which may be in different geographic regions. If the primary Vault
Group becomes unavailable, because of network, power, or other catastrophic problems, any Streamer
or Caching Node that was requesting content from that Vault Group would fail over to the other Vault
Group until the primary Vault Group came back online and could again respond to cache-fill requests for
content.
With Vault redundancy, at least one copy of each content within a group is mirrored to a configured peer
group. Vault Group mirroring runs as a low-priority process, so as not to impact the performance of the
guaranteed streaming delivery.
Note The maximum number of Vault Groups is 20.
Streamer Disk Redundancy
The disks in the Streamer are not used for full content storage as in most VOD implementations. Rather,
the Streamer disks are part of the TV CDS multilevel caching architecture. If a disk is lost on a Streamer,
the only impact is a marginal loss of caching capability for the system. Any content that was cached on
that Streamer disk is retrieved again from the Vault. The RAM on the Streamer has enough content
cached for streaming to the subscriber, so that this refetch of content from the Vault occurs without
impacting the subscribers. For example, for a Streamer array of five Streamers with sixteen hard drives
each, a lost drive only reduces the total caching capability by less than 1.25 percent. The need to replace
the failed drive is not time critical in the least, making quarterly replacement of any failed Streamer
drives feasible.
Streamer Server Resiliency
The Cisco TV CDS architecture allows for failed Streamer servers as well. If any Streamer server fails,
the communication to the backoffice is transparently handed off to another Streamer. With the TV CDS
software, if a Streamer server fails the other Streamers recognize that failure and continue streaming to
that subscriber.
Caching Node Disk Redundancy
The disks in the Caching Node are not used for full content storage like most VOD implementations.
Rather, the Caching Node disks are part of the TV CDS multilevel caching architecture. If a disk is lost
on a Caching Node, the only impact is a marginal loss of caching capability for the system. Any content
that was cached on that Caching Node disk is retrieved again from the Vault.
Caching Node Resiliency
The Cisco TV CDS architecture allows for failed Caching Nodes as well. If a Caching Node fails, any
cache-fill transmissions that were in process at the time of the failure are re-requested by the Streamer,
and any new requests are responded to by the remaining Cache Nodes in the Cache Group.