Zfs heavy io writing | zfskern txg_thread_enter

Steven Hartland killing at multiplay.co.uk
Fri Feb 19 12:29:40 UTC 2016

On 19/02/2016 11:58, Michelle Sullivan wrote:
> Niccolò Corvini wrote:
>> Hi, first time here!
>> We are having a problem with a server running FreeBsd 9.1 with ZFS on a
> You should upgrade to a supported version first...  9.3 would probably
> be the best (rather than 10.x) as it's still supported and uses the same
> ABI (ie you should need to reinstall all your ports/packages - though
> you should because it sometimes breaks things - at least check for
> broken things :) .)
> If you're not familiar "freebsd-update -r 9.3-RELEASE upgrade" will help
> you do it without too many problems.
9.3 is still ancient, and while "supported" its not in active 
development, and to be blunt no one will be interested in helping to 
diagnose any actual issue on something so old.

10.x has a totally different ZFS IO scheduler for example, so its 
differently for most workloads.
>> single sata drive. Since a few days ago, in the morning the system becomes
>> really slow due of a really heavy io writing. We investigated and we think
>> it might start at night, maybe correlated to to crondaily (standard) but we
>> are not sure.  After a few hours the situation returns to normal.
> Yeah this sounds like something I am quite familiar with...  It's the
> security check cronjob that runs every day... its looking for any
> setuid/setgid files, new/modified files...etc... across all file systems
This is quite likely, so while updating to 10 may not fix the issue 
running on 9.x.

Be aware that 10.3-BETA2 has a known issue related to vnode memory usage 
which can be triggered by such workloads so trying BETA3 when released, 
which should address this would be a good idea.


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