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Media Flow Controller Hierarchical Caching 49
Media Flow Controller Administrator’s Guide Media Flow Controller Overview
Media Flow Controller Hierarchical Caching
When Media Flow Controller fetches data from origin upon cache miss, it caches the data in its
local disks. Media Flow Controller implements an hierarchical caching mechanism that allows
it to serve up to 10Gbps of data with just 16GB of RAM and a combination of SSD, SAS, and
SATA storage. Media Flow Controller has its own optimized storage sub-system in which data
is placed intelligently so it can be read back for very fast delivery to end-users.
Media Flow Controller organizes data in a hierarchical fashion using a cache tier manager that
dynamically calculates the “hotness” of the data and places it in the right cache tier (see
““Hot”
Content (Short Tail vs. Long Tail)” on page 31 for explanation of hotness). RAM is the highest
tier, followed by SSD, SAS, and SATA, in that order.
Disk speeds are calculated and assigned to a tier in the cache hierarchy as part of the
initialization of Media Flow Controller. When data is accessed from origin, it is stored in the
lowest cache tier, and promoted to higher cache tiers as the hotness of the data increases. All
this is done automatically by Media Flow Controller.
Additionally, Media Flow Controller allows you to configure cache ingestion and promotion
parameters (cache-ingest size-threshold and cache-promotion hotness-threshold) via
the
analytics command to create policies for when to ingest, or promote, hot objects to cache
or the next highest cache tier, respectively. See “Terminology” on page 30 for definition of
“ingest.”
See Figure 3 , for an illustration.
Figure 3 Media Flow Controller Cache Ingest and Promotion Process