There are lots of factors that determine the system health of a server. The hardware capabilities - CPU, memory or disk - is an important one, but also the server load - number of devices (Nodes to be polled, updated, audited, synchronised), number of products (NMIS, OAE, opCharts, opHA - each running different processes), number of concurrent users. 

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• Scaling NMIS Polling
• Scaling NMIS polling - how NMIS handles long running processes
• Configuration Options for Server Performance Tuning

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Opmantek

Before Start

The first thing to do will be get the information of out our system:

• System Information: NMIS and OMK support tool will give us all the information needed.
• Monitor services: NMIS can monitor the involved processes - apache2, nmis9d, omkd and mongod - and provide useful information about CPU and memory - among others. 

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omkd_max_requests

MongoDB memory usage

MongoDB, in its default configuration, will use will use the larger of either 256 MB or ½ of (ram – 1 GB) for its cache size.

MongoDB cache size can be changed by adding the cacheSizeGB argument to the /etc/mongod.conf configuration file, as shown below.

storage:
  dbPath: /var/lib/mongodb
  journal:
    enabled: true
  wiredTiger:
      engineConfig:
         cacheSizeGB: 1

Here is an interesting information regarding how MongoDB reserves memory for internal cache and WiredTiger, the underneath technology. Also some adjustment that can be done: https://dba.stackexchange.com/questions/148395/mongodb-using-too-much-memory

Server examples

Two servers are compared in this section.

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System information:

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