On 2017-03-22 16:02, O. Hartmann wrote:
> CURRENT (FreeBSD 12.0-CURRENT #82 r315720: Wed Mar 22 18:49:28 CET 2017 
> amd64) is
> annoyingly slow! While scrubbing is working on my 12 GB ZFS volume, updating 
> /usr/ports
> takes >25 min(!). That is an absolute record now.
> I do an almost  daily update of world and ports tree and have periodic 
> scrubbing ZFS
> volumes every 35 days, as it is defined in /etc/defaults. Prts tree hasn't 
> grown much,
> the content of the ZFS volume hasn't changed much (~ 100 GB, its fill is 
> about 4 TB now)
> and this is now for ~ 2 years constant. 
> I've experienced before that while scrubbing the ZFS volume, some operations, 
> even the
> update of /usr/ports which resides on that ZFS RAIDZ volume, takes a bit 
> longer than
> usual - but never that long like now!
> Another box is quite unusable while it is scrubbing and it has been usable 
> times before.
> The change is dramatic ...
> Regards,
> Oliver

Due to differences in the kern.hz setting between IllumOS and FreeBSD,
the result is FreeBSD doesn't de-prioritize scrub I/O as much as IllumOS

sysctl vfs.zfs.scrub_delay=40

This will speed for 40 ticks (40ms on FreeBSD), between each scrub I/O,
allowing your ports update to proceed more quickly.

'zpool list' will show how fragmented your pool is, and how full it is,
these may also provide insight.

If you run 'top -S' while it is performing badly, what is the CPU load like?

Is your /usr/ports dataset compressed?

Allan Jude

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