Check manual page of zfsget

ZFS Pools/Filesystems: Used Space
Distribution official part of Check_MK
License GPL
Supported Agents Linux Solaris Freebsd

This check monitors the usage of ZFS filesystems using the output of the command {zfsget}. This is done in a separate check since the output of {df} does not show the required metrics when ZFS is used with quotas. The check is fully compatible with {df} with respect to its configuration, output and logic. Please refer to the manual of {df} for details. ZFS has some specialities when compared with "normal" filesystems. From the point of view of monitoring the crucial difference is that several filesystems live together in a common "pool". Each of the filesystems has its own amount of used space. But they share a common free space. If you want to compute the {percentage} of used/free space of a filesystem, you may run into trouble. Let's take the following example: Lets say we have a pool P of the size 10GB where the filesystems A and B live. Lets assume that A currently uses 2GB and B uses 7GB. That makes 1GB left available in the pool. Reporting 20% usage for A would be misleading in such a case, because you would assume 80% (i.e. 8GB) of free space. But in fact just 1GB is left free for futher files. For that reason our {zfsget} check reports the current usage plus the available pool space as total size of the filesystem. In our example that means that the "size" of A is reported as 3GB with 2GB used (which makes 66.6%). That way all filesystems will become critical if the available pool space goes to zero. Filesystems with a {quota} are handled differently, however. Here the quota is reported as the total size. If A has a quota of 5GB, we report 2GB out of 5GB used.

Item

The mountpoint of the filesystem

Discovery

One service is created for each mountpoint.