Running Observer Without Reserved Memory - Network Instruments GigaStor User Manual

Selecting an appropriate capture buffer size given system resources is all most users need to worry about; the
default settings for the statistical buffers work perfectly fine in the vast majority of circumstances.
However, if you are pushing the limits of your probe system by creating many probe instances, you may be able
to avoid some performance problems by fine-tuning thememory 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'smemory constraints if you set
up the statistics buffers to only allocate memory for tracking Top Talkers and to not allocatememory 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 probe instances doing packet captures.)
Use this formula to determine your RAM buffer size:
Network Speed
× Average Throughput (MB/second)
Seconds of data storable in RAM
Tip!
You want a buffer that will handle your largest, worst case unfiltered burst.
Use this formula to determine how much hard drive space a capture requires (in GB) and Observer's write-to-disk
capability. There is no limitation to the amount dataObserver can write to disk other than the disk size itself.
(Traffic Level / 8 bit) × 3600 Seconds
÷ 1024 bytes
Gigabytes per hour
For instance a fully utilized 1 Gb port (1 Gbps is 125 MBps):
(125 MBps / 8 bit) × 3600 Seconds
÷ 1024 bytes
~54.93 GB per hour

Running Observer without reserved memory

Single probes cannot use reserved memory. By default, no memory is reserved for Observer if you install it on
your own system.
Prerequisite(s):
All versions of Observer Expert, Observer Suite, Expert Probe software, and Multi Probe software
installed on your own hardware, unless modified.
Single Probe software at all times
NetFlow probes
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