Network Instruments GigaStor 114ff - Manual (Page 55)

Packet capture buffer and statistics buffer
Chapter 3 Packet Capture or GigaStor Capture
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However, if you are pushing the limits of the system on which the
probe is installed by creating many probe instances, you may be able
to avoid some performance problems by fine-tuning the memory
allocation for each probe instance.
For example, suppose you want to give a number of remote
administrators access to Top Talkers data from a given probe. You will
be able to add more probe instances within a given system’s memory
constraints if you set up the statistics buffers to only allocate memory
for tracking Top Talkers and to not allocate memory for statistics that
no one will be looking at.
Observer has no limitations on the amount of RAM that can be used
for a buffer.
You can allocate up to 4 gigabytes, limited only by the physical
memory installed on your Windows system. Note that when run on a
64-bit Windows, there is no 4 GB limitation for the capture buffer;
you are limited only by the amount of physical memory installed on
the probe.
In all cases, the actual buffer size (Max Buffer Size) is also reduced by
7% for memory management purposes. Should you try and exceed the
Max Buffer Size an error dialog will be displayed indicating the
minimum and maximum buffer size for your Observer (or probe)
buffer.
For passive probe instances, which are most often used for
troubleshooting, the default settings should be sufficient. If you are
creating an active probe instance (one that writes to disk and not just
reads from it), then you may want to use the following formula as a
rough guideline to determine how much RAM to reserve for the
probe instance when doing a packet capture. (This formula does not
apply when doing a GigaStor capture to disk. It is only for passive
probe instances doing packet captures.)
T IP ! C APTURE
B UFFER
You want a buffer that will handle your largest, worst case
burst.
Network Speed × Average Throughput (MB/second) = Seconds of data storeable in RAM