24 Multi-role Recorders User Guide (HW/BK/0034 | 12 Oct. 2021)
3
For details, refer to the “Setting the multicast address filter” table in
TEC/NOT/069 - Xbar Switches - Filtering and
and the appropriate multi-role recorder data sheet for details on the number of filters and filter types
available.
N
OTE
:
The multi-role recorder does not support the use of multicast IP addresses of the format XXX.0.0.0.
File formats and management
Formatting the media creates pre-allocated empty files for storing recordings in a flat directory structure. The
purpose of formatting the media is to allow the multi-role recorder to record in contiguous locations on the media
and to ensure that no other files are stored or created on the media.
Formatting files
The number of pre-allocated files that are created during the formatting process is a function of the total memory
media capacity. For example, a formatted 24 GB CF card comprises 200 pre-allocated files where each file is
120 MB.
Using the
defaultFileSize
SNMP variable, you can set the default file size for files generated, and therefore
the number of files created during the pre-formatting process, using one of the following options:
•
Many small files
: this has the advantage of less wasted space each time START/STOP is pressed but
requires more file management and re-assembly when the data is analyzed.
•
Few large files
: this is suited to applications where there is continuous recording of the data with few
START/STOP triggers.
The number of files that are created is a function of the default file size and the capacity of the memory media. If
the
defaultFileSize
SNMP variable is set to zero, the multi-role recorder sets it automatically based on the
capacity of the media mounted. This setting can be configured using SNMP (for more information on using SNMP
see
TEC/NOT/058 - Overview of SNMP and using third party SNMP tools
).
Opening and closing of files
When START/STOP switch moved to START position
A new file is always opened when recording starts. When recording starts, the next unused empty file is opened. If
the media has just been formatted prior to recording, this is the first file on the media. If the media already contains
recording files, it is the next unused file in the directory.
During recording
Ethernet frames are written to the current open file until it is full and then the following happens:
•
The file is closed.
•
The file attributes are updated for the closed file.
•
The next unused file is opened for recording.
In this way, Ethernet frames are written contiguously into the files, and the files are used contiguously on the
media.
When START/STOP switch moved to STOP position
When the recording is stopped, the current file is closed and the file attributes are updated to indicate the <date>
<time> <attributes> <file size> <file name>. The file size is the actual size of the file. For example, consider that the
pre-formatted space files have a maximum size of 120 MB, if only 10 MB of data has been written into the file when
the recording is stopped, the file size indicates that the file is 10 MB. However, it should be noted that although the
file is only 10 MB in size, it still occupies 120 MB of space on the media, which results in 110 MB of wasted space.
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