=== Ztop

Links: +
link:https://github.com/asomers/ztop[Repository] +
link:https://www.freshports.org/sysutils/ztop[Port] +

Contact: Alan Somers <asomers@FreeBSD.org> +

`ztop` is a new utility that displays ZFS datasets' I/O in real time, like
`top`, but for ZFS.  Unlike the existing `zpool iostat`, which only displays
traffic at the level of a pool, `ztop` displays it at the level of individual
datasets.

Previously, there was no tool that could display this information.  The
link:https://github.com/prometheus/node_exporter/pull/1632[Prometheus Node
Exporter] can export it into Prometheus, from which it can be viewed
after the fact with various other tools, but that requires a large stack of
software, and isn't real-time.

I started `ztop` this quarter, and it is now fully functional.  However, it has
revealed a performance problem within the kernel.  In the presence of more than
a few thousand datasets, the sysctl interface is too slow and `ztop` becomes
sluggish.  Future work, if I have the time, will address that problem.

Sponsor: Axcient