ZFS filesystem full and logs

[Matthew Seaman]

On 03/07/2019 08:57, Andrea Venturoli wrote:
> When using UFS, if a filesystem gets full, this is logged via syslogd.
> Can the same happen somehow for ZFS?
> If it's possible, how is it done?

ZFS doesn't fill up file systems: it fills up pools[*].  If your entire 
zpool is full up, then you'll know about it PDQ, as your machine will be 
a very unhappy bunny.  However, because your zpool will (in general) 
have access to all of the available space on your hard drives, you're 
going to see a lot fewer problems with space usage than if you're 
dealing with a bunch of UFSes each fixed at just a fraction of your 
total available space.

If the entire pool does fill up, you won't be able to write anything via 
syslog(8) anyhow.

Keeping on top of disk usage is a standard task for system monitoring 
(nagios, icinga, many more) and most people would also make graphs 
showing usage over time (grafana, cacti, various others).  If that's a 
bit too heavy-weight for you, then you could write a small periodic 
script to run every day and alert you in the daily e-mails if disk usage 
has hit whatever predefined limits you choose.

	Cheers,

	Matthew

[*] Unless you set size limits on specific ZFSes...