Managing media assets

Bernie Walsh looks at some of the considerations for designing a central storage system and the consequent technical issues that need to be addressed.

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By  Bernie Walsh Published  April 13, 2008

Bernie Walsh looks at some of the considerations for designing a central storage system and the consequent technical issues that need to be addressed.

We have now achieved a certain level of maturity in the way we view digital broadcasting technology. First we had individual digital applications, usually at the high end of post-production.

From there, we have grown to a widespread use of digital acquisition, editing and manipulation, albeit often using proprietary formats and interconnecting through a dedicated video-style interface: SDI.

By saying we have reached a certain level of maturity, I mean that we are finally recognising digital video and audio files for what they really are: data. As a succession of 1s and 0s, they are identical to any other data in any other computer application.

We need to treat them as such. Imagine for a moment a world where your spreadsheets needed to run on separate computers, networks and servers from your email; where documents in Microsoft Word needed to be decoded to raw ASCII before they could be passed on to someone else. This is clearly unacceptable.

Once you have a facility-wide system that can exchange digital files as data, with each broadcast application being able to share common content, then the logical step is to provide a central store for that content. But what are the considerations for designing a central storage system, and what are the technical issues that need to be resolved?

Layered storage

The traditional IT approach to centralised storage is to create a hierarchical view of the system, broadly speaking:

Online - expensive spinning disks with very high throughput for immediate delivery of data.

Nearline - less expensive spinning disks, which can move content to the online server quickly when required.

Archive - a tape or optical disk library system which takes content from the nearline disks when capacity is an issue.

Offline - shelved storage of tapes or optical media when the archive system is full.

From top to bottom, those four levels decrease in convenience and speed of access, but also decrease in cost. The art of the system designer is to get the right capacity at each stage to meet the service level requirements at the minimum cost.

System architecture

A central storage system will normally be spread across multiple layers. The broadcast application itself - editor or playout server, for example - will have its own local storage.

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