This article applies as of PRTG 25
SNMP Linux Block Device I/O
The SNMP Linux Block Device I/O sensor monitors the input/output (I/O) of a block device on a Linux system using the Simple Network Management Protocol (SNMP).
The first time you create this sensor, PRTG runs a meta-scan to detect all block devices on your server. It uses objects from the diskIOTable in the UCD-DISKIO-MIB Management Information Base (MIB) module to detect what kind of values are available to monitor. Specifically, the sensor looks for the following SNMP objects and maps them to sensor channels:
| SNMP Objects | Description | Channel |
|---|---|---|
| diskIONReadX diskIOWrittenX | 64-bit values | Bytes Read Bytes Written |
| diskIONRead diskIONWritten | 32-bit values | Read Accesses Write Accesses |
| diskIOLA1 diskIOLA5 diskIOLA15 | Load average percentage over time | Load Average (1 Minute) Load Average (5 Minutes) Load Average (15 Minutes) |
The settings that the sensor displays and the channels that the sensor creates depends on your Linux system setup and which SNMP version you use.
What happens when I change SNMP versions?
If you change your SNMP version after you create an SNMP Linux Block Device I/O sensor, the sensor might fail to display correct monitoring data. Because the meta-scan only runs once during sensor creation, PRTG does not detect changes in available values after sensor creation. As a result, existing sensors continue to use the original value that PRTG detected upon creation, even if those values do not exist anymore or new values are available.
To ensure that you continue to receive correct monitoring data, you can either create new sensors or manually update the settings of your existing sensors. We recommend that you update your existing sensors to maintain historical data.
See the examples below on how to update your existing sensor settings.
Example 1 - You change from an SNMP version that does not support 64-bit values to one that does. |
You created an SNMP Linux Block Device I/O sensor with SNMP v1 credentials, for example, so PRTG only detects 32-bit values when it runs the meta-scan. You update your SNMP credentials to SNMP v2 or SNMP v3, which support 64-bit values load average values. The sensor continues to show the 32-bit values. To get the sensor to use the 64-bit values, manually set 64-Bit Values Available to Yes in the Specific Sensor Settings. |
Example 2 - You change to an SNMP version that does not support 64-bit values. |
You created an SNMP Linux Block Device I/O sensor with an SNMP version that supports 64-bit values. When you update your SNMP credentials, 64-bit values are no longer available. As a result, the sensor no longer displays new values for the relevant channels. To get the sensor to use 32-bit values, you must manually set 64-Bit Values Available to No in the Specific Sensor Settings. |
