Visual Circuits Harmony 4E, User Manual

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21
D
UAL
-C
ARD
S
ERVERS
Multi-Threading and Drive
Mapping
Depending on hard drive speed and bitrate, proper drive mapping
can be crucial for MPEG playback performance. Fundamentally,
this often involves configuring the driver so that it reads from
different physical hard drives simultaneously. In a system with two
MPEG content hard drives, data should be read from both drives at
the same time for maximum performance.
The MaxDisks driver parameter is used to specify the number of
playback storage hard drives used in a system. The driver will
divide the available playback channels into MaxDisks groups and
each group will perform concurrent reads (in software terms, each
group will have a separate “thread of execution”). Therefore, each
group of channels should read files from a different physical hard
drive. You must configure your application so that MPEGs are
read from the correct drives by the correct channels.
If MaxDisks is left at the default value of 1, reads from all the hard
drives will be sequential. That is, only one read of MPEG data will
be performed at a time. This is normal for a single content drive.
However with multiple drives, a read from one drive will have to
be completed before a read on another drive can be initiated. This
situation does not take advantage of the performance potential of a
multi hard drive system.
It is actually permissible that a channel group reads from a set of
physical hard drives, as long as none of the drives in the set belong
to another channel group. This is beneficial if the MPEG files will
not all fit on a single drive. For simplified mapping, it is
recommended to divide the numbers of channels evenly and
sequentially across multiple boards.