VBrick dme Admin Manual page 98

The caching system on the DME, which is independent from the content directories, is
stored either in Memory or on Disk. These caches are maintained, and content is aged out by
the caching system.
Depending upon your specific needs for this particular DME, you may wish to increase or
decrease the caching capabilities. Specifically, you can control how much memory and disk
the caching system can utilize. These settings control only HTTP based protocol caching
(which includes progressive mp4, HLS and HDS delivery). Each of these settings will also
have an impact on the amount of available storage for VOD content. Further, extensive use
of the CPU will have a trade-off effect with other CPU intensive features (like transrating).
As such, High or Dedicated settings should only be used on DMEs that will be used as
reflectors or purely caching. DMEs that are used as prepositioned content servers should be
set with Normal to Low caching settings.
This setting is unique to each of your DMEs within your deployment. As an example, it may
be, based on your deployment architecture, that a few edge DMEs will be set as High
Caching to facilitate remote reflection, while larger content DMEs may be set for Normal or
Low. Please consider this setting during your deployment architecture design.
The table below defines the memory and disk allotments (what is available to be used as a
percentage of system resources) by usage level (Dedicated, High, Normal, or Low – as
selected and defined by the Cache System Resources (Memory/Disk) Used: setting within the
DME.) These allotments are consistently applied across all DME versions, e.g., Large DMEs
set to High will use the same percentage of memory (30%) as a Small DME set to High.
These percentages are based off the memory within the system, so any over- or under-
provisioning within VMs will be reflected in the allotment. The table also defines a minimum
setting (or floor) for each of the values.
These allotments are based on a 75%/25% rule of use that prioritizes in-memory cache use
over on-disk cache use. In other words, the DME reserves up to 75% of allowable memory
(based on the chart below) for in memory objects, while the remaining 25% is used for
indexes of on-disk caching. By limiting our disk cache index use to 25%, we have also
reduced the addressable on-disk cache. This rule has had an reduction impact on the size of
disk cache, as compared to older DME versions, but still represent a sizable use of storage
depending on usage level.
These settings can be configured on the System Configuration > Streaming page in the
Cache System Resources Used drop-down.
Memory
Disk
Tip: Your system Cache (both memory and disk) can be cleared by the Clear
Cache button on Maintenance > System Maintenance page.
Please see the System Maintenance topic for details.
Standalone DME or Legacy (DME with VEMS) Caching Configuration
86
Dedicated
Allowable Use 50%
Minimum Setting 512 MB
Allowable Use 14.5%
Minimum Setting 8192 MB
High Normal
30% 12.5%
256 MB 200 MB
8.6% 3.5%
4096 MB 2046 MB
© Vbrick Systems, Inc.
Low
6.25%
100 MB
1.7%
1024 MB