Disk monitoring Inconsistency [Problem]

[apachi]

I have two different data

1. CentOS Linux release 7.7.1908 (Core)
df -h

Disk size



2. Zabbix 5.4.3. © 2001–2021,
Monitoring Disk space usage



What could be the reason why there is a difference?

thx

[ISiroshtan]

Well if you do simple math, you would find the answer.

Zabbix calculates free space as 126.6/157.36 = 80.45% - matches what you see.

Now if we take numbers from free.
Calculate % based on used space - 127/158 = 80.37%, - we can assume free calculates it not this way, but it matches data from Zabbix
Calculate % based on free space - 100 - (23/158)*100 = 100 - 14.55 = 85.44% - matches what free shows, so that's how it's calculated.

Why difference tho? Lets check data from free: 127 used + 23 free = 150 GB. But actual disk size is 158 GB. So free does not account some 8GB. Sadly can not say why it does so,

Hope it helps mate.

[tim.mooney]

Why difference tho? Lets check data from free: 127 used + 23 free = 150 GB. But actual disk size is 158 GB. So free does not account some 8GB. Sadly can not say why it does so,

Most Linux filesystems emulate a behavior that was common on Unix filesystems: "reserved" space. When a filesystem is created, you can decide how much space is set aside for "reserved space" (it can be adjusted for most filesystems using "tunefs", or tune2fs on Linux), that is only usable by processes running as the 'root' user.

The discrepancy the 'df' command shows is because it doesn't account for this "reserved space". The reserved space is often called "minimum free space" or frequently on Linux, just "minfree".

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