Document Number: OSUP1046
Product: Observer 9.x or greater
Date: 4-2-2004
Title: Network Trending & Internet Trending Disk Usage

Observer's Network Trending and Internet Trending features store network data as efficiently as possible; this support document provides guidelines on how much disk space each of these features will consume given the network under analysis and the collection interval.  

The network parameters that affect the amount of data collected each interval are the number of stations and the number of protocols sensed on the network.

Network Trending Disk Usage
In addition to a 176 byte header, Network Trending writes 184 byte record for every station each collection interval. If Protocols by Station is enabled, each station record grows an additional 32 bytes per protocol observed on that station. Click Settings on the Network Trending dashboard and then the Network Trending Specific tab to enable or disable Protocols by Station. 

For a 100-station network running an average of a dozen protocols, the formula to determine how much data gets written each collection interval is:

which equates to 56976 bytes, or approximately 57K each collection interval. The table below shows how much space is consumed given different collection intervals. The table also assumes that collection is turned on 24 hours per day, 7 days a week. You can set the data collection schedule to limit disk consumption to the times you are interested in from the Network Trending Settings dialog's Data Collection tab.

Internet Trending Disk Usage
When running Internet Trending, Observer writes a 56 byte record for each IP Station. If Internet Patrol is enabled, each station pair generates another 56 byte record. IP Protocols generates 48 bytes per station, plus another 32 bytes per station for each active protocol. Each one of these features can be enabled or disabled by clicking on Settings from the Network Trending dashboard, and then the IP Specific tab. 

If all of these features are enabled on a 100- station network averaging 10 protocols per station, with a 60% of the stations having IP conversations at any one time, the formula to determine how much data will get written every collection period is:

Which is 28800 bytes, or approximately 29K each collection interval.  Because IP Trending has a fixed collection interval of 10 minutes, the daily disk usage for IP Trending would be about 4.2MB, or about 126MB per month.