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Zabbix Free Disk Space Is Less Than 20 On Volume – Let’s fix it

Oops!! Frustrated with Zabbix free disk space is less than 20 on volume alert?

Monitoring systems like the Zabbix gives this alert when server disk space usage crosses 80%.

High disk space usage eventually can affect the working of mail services, database servers, etc.

That’s why at Bobcares, we get emergency requests regarding Zabbix disk space alerts, as a part of our Server Management Services.

Today, we’ll see how our Support Engineers act upon the Zabbix alert for our customers.


What is this Zabbix Free Disk Space Is Less Than 20 On Volume alert?

In general, Zabbix greatly helps in monitoring the servers. Zabbix triggers alerts to indicate upcoming problems on the server.

One such alert is this free disk space less alert.

The trigger gives this alert when the disk space is less than 20%  on the volume. Here, the Zabbix allows customization on the threshold at which the system triggers the alert.

Moreover, based on the purpose of the server, we see some customers set it at even low values like 10%. A snippet of Zabbix dashboard with such alerts show up as:


Low free disk space is a critical alert on the server. This is because, when the server is running out of disk space, all disk writes fail. This means it cannot fetch emails, updated databases, etc. This, in turn, causes mail failure, website down, etc.

In such situations, we firstly find out what is consuming the disk space and take action accordingly.

Let’s see how our Engineers found a fix for this Zabbix message.


How do we fix disk space?

From our expertise in managing servers, we see many reasons for high server disk space usage. This can be large logs, huge website content, backup files, etc.

Let’s now check the top causes for high disk usage.


1. Large log files

In many cases, large log files cause a free disk space shortage in servers.

Recently, one of our customers approached us saying that he was getting an alert “Free disk space is less than 20% on volume /” in his Zabbix.

So, our Engineers checked in detail and found that 86% of the filesystem mounted on / was already used. Only 2.8G out of 20G was remaining and that’s why Zabbix triggered such an alert.

Zabbix Free Disk Space Is Less Than 20 On Volume

Next, we searched for what is consuming that much space. And our search reached the access log. We found that the size of access logs was really high and those are consuming 80% of disk space.

Apache access logs were taking more space, especially one of the old access logs that had a size of 5.6GB.

Our Dedicated Engineers did a deeper dig for finding a solution for this and they finally found a misconfiguration in log rotation.

In Linux, all the logs are noted, compressed and rotated by logrotate utility. It is a log file manager.

So, we had to tweak the delaycompress parameter in the corresponding file under /etc/logrotate.d. This fixed the problem.


2. Big Home directory

Likewise, a big home directory of the user can also create a disk space problem in the server. Website users tend to save too much content on their servers, large backups, old emails, etc. As a result, server disk space usage goes high.

That’s why our Dedicated Engineers periodically audit the servers for disk space usage. Additionally, we set up Zabbix alerts to monitor disk space triggers.


3. Installation Left-overs

Similarly, we often see bad software installation practices also shoot up server disk space usage. Major triggers here include not removing failed install files, keeping partially restored backups, multiple old backups, and many more.

Therefore, we always make sure to check for such files on the triggering of disk space usage alert.


[Having trouble in fixing Zabbix errors? – Our Experts are available 24/7.]



In short, we discussed the reasons for Zabbix Free Disk Space Is Less Than 20% On Volume alert and saw how our Support Engineers resolve it for our customers.


Never again lose customers to poor server speed! Let us help you.

Our server experts will monitor & maintain your server 24/7 so that it remains lightning fast and secure.


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