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snmp_linux_meminfo_sensor --available memory

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Hi,

We are using linuxmeminfo sensor, however the available memory seems to be showing wrong values.

SNMP Linux Meminfo Sensor

eg: Available Memory is shown as 351MB, when in fact it is 5.7G. It is taking from free rather than available.

$ free -h

              total        used        free      shared  buff/cache   available
Mem:           7.6G        1.7G        351M         30M        5.6G        5.7G
Swap:          2.0G         34M        2.0G

more /proc/version

Linux version 3.10.0-229.14.1.el7.x86_64 ([email protected]) (gcc version 4.8.3 20140911 (Red Hat 4.8.3-9) (GCC) ) #1 SMP Tue Sep 15 15:05:51 UTC 2015

Is this expected functionality or error in sensor.

thanks

meminfo prtg snmp

Created on Dec 21, 2015 3:24:11 AM by  nkarnati (0) 1

Last change on Dec 21, 2015 7:32:21 AM by  Luciano Lingnau [Paessler Support]



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The values displayed by the sensor are correct, but please mind that they only consider real free memory while not taking in account cached and buffered memory.

For alternate readings, please use the SNMP Library Sensor with the Basic Linux Library.

Another alternative is to deploy the SNMP Custom Sensor or SNMP Custom Advanced Sensor using one of the following OID's:

DescriptionOID
The total amount of swap space configured for this host1.3.6.1.4.1.2021.4.3.0
The amount of swap space currently unused or available1.3.6.1.4.1.2021.4.4.0
The total amount of real/physical memory installed on this host1.3.6.1.4.1.2021.4.5.0
The amount of real/physical memory currently unused or available1.3.6.1.4.1.2021.4.6.0
The total amount of memory free or available for use on this host1.3.6.1.4.1.2021.4.11.0
The total amount of real or virtual memory currently allocated for use as shared memory1.3.6.1.4.1.2021.4.13.0
The total amount of real or virtual memory currently allocated for use as memory buffers1.3.6.1.4.1.2021.4.14.0
The total amount of real or virtual memory currently allocated for use as cached memory1.3.6.1.4.1.2021.4.15.0

With both of the above mentioned sensor you should be able to get all memory related information.

Additionally, if you need to see values in Percent, set-up an Sensor Factory Sensor to perform the required mathematical operations on top of the results of the SNMP sensors.

Created on Dec 30, 2015 7:54:12 AM by  Luciano Lingnau [Paessler Support]

Last change on Oct 19, 2017 2:22:54 PM by  Luciano Lingnau [Paessler Support]



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Hello nkarnati,
we appreciate your contact.

Please download our latest SNMP Tester, run it on the PRTG Host (or host of the Remote Probe), and perform a Walk against the target device providing the "1.3.6.1.4.1.2021.4" OID (without quotes) as parameter.

Which results do you get in the Tester? Please report back with the results from the tester.

Best regards,

Created on Dec 21, 2015 7:36:14 AM by  Luciano Lingnau [Paessler Support]



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ok.. found seems to be issue with Linux Meminfo sensor.

Created on Dec 30, 2015 2:48:47 AM by  nkarnati (0) 1

Last change on Dec 30, 2015 7:55:27 AM by  Luciano Lingnau [Paessler Support]



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The values displayed by the sensor are correct, but please mind that they only consider real free memory while not taking in account cached and buffered memory.

For alternate readings, please use the SNMP Library Sensor with the Basic Linux Library.

Another alternative is to deploy the SNMP Custom Sensor or SNMP Custom Advanced Sensor using one of the following OID's:

DescriptionOID
The total amount of swap space configured for this host1.3.6.1.4.1.2021.4.3.0
The amount of swap space currently unused or available1.3.6.1.4.1.2021.4.4.0
The total amount of real/physical memory installed on this host1.3.6.1.4.1.2021.4.5.0
The amount of real/physical memory currently unused or available1.3.6.1.4.1.2021.4.6.0
The total amount of memory free or available for use on this host1.3.6.1.4.1.2021.4.11.0
The total amount of real or virtual memory currently allocated for use as shared memory1.3.6.1.4.1.2021.4.13.0
The total amount of real or virtual memory currently allocated for use as memory buffers1.3.6.1.4.1.2021.4.14.0
The total amount of real or virtual memory currently allocated for use as cached memory1.3.6.1.4.1.2021.4.15.0

With both of the above mentioned sensor you should be able to get all memory related information.

Additionally, if you need to see values in Percent, set-up an Sensor Factory Sensor to perform the required mathematical operations on top of the results of the SNMP sensors.

Created on Dec 30, 2015 7:54:12 AM by  Luciano Lingnau [Paessler Support]

Last change on Oct 19, 2017 2:22:54 PM by  Luciano Lingnau [Paessler Support]



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yes, this is useful, however we are interested in percentages as absolutely values are not useful.

Do you have any other alternative to get the same values mentioned above as percentage (i.e use out of box and doesn't require to install any scripts).

i.e:

  • Available Swap Space %
  • Total RAM used %
  • Total RAM Free %
  • Total RAM Shared %
  • Total RAM Buffered %
  • Total Cached Memory %

Thanks

Created on Dec 30, 2015 8:32:08 AM by  nkarnati (0) 1

Last change on Dec 30, 2015 9:47:28 AM by  Luciano Lingnau [Paessler Support]



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Have you tried using the standard SNMP Memory Sensor?

The main difference is that while the SNMP Linux Meminfo Sensor queries the 1.3.6.1.4.1.2021.4.xx OID's from the UCD-SNMP-MIB the SNMP Memory Sensor queries the hrStorageTable from the HOST-RESOURCES-MIB, which will most likely display different values.

If that doesn't show you the expected/desired result, the only remaining option which doesn't involve scripting involves using the Sensor Factory Sensor to convert the SNMP values from other sensors to a result in percent.

Best Regards,

Created on Dec 30, 2015 12:01:56 PM by  Luciano Lingnau [Paessler Support]



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Disclaimer: The information in the Paessler Knowledge Base comes without warranty of any kind. Use at your own risk. Before applying any instructions please exercise proper system administrator housekeeping. You must make sure that a proper backup of all your data is available.