CDM Disk usage percentage on Linux: discrepancy between df command and metric collected

Products

• DX Unified Infrastructure Management (Nimsoft / UIM)

Issue/Introduction

I'm seeing a discrepancy between how CDM is calculating / collecting disk usage for my linux partitions and the correspondent "df" command ran on the machine. 

For example, use % in df is 6% while the probe collects 5.54%. 

How is CDM calculating QOS_DISK_USAGE_PERC  on linux?

Why do I see a discrepancy between the "df -hp" command and the collected QOS? 

Environment

• DX UIM 20.4.*
• CDM any version
• Linux

 

Cause

CDM probe does not use df command

Resolution

The difference between DF and the collected metrics is expected as CDM does not use "df". 

"The list of mounted filesystems is found using the system call getmntent(). Space usage 
on the filesystems is found using the system call statvfs()." 

See page 11 at the CPU, Disk and Memory probe (cdm) Technical Brief 

These are system-level calls, not commands.  So then based on the data, CDM is doing the calculations and collecting the corresponding metric.

Additional Information

CPU, Disk and Memory probe (cdm) Technical Brief