[ZFS] ARC accounting bug ?

[Ben RUBSON]

I'm sorry but I still can't find out where do these ARC demand metadata misses come from.
In addition, why they are not cached, as my ARC is 1% used.
And why I don't see any disk activity to honour them.

I would really be glad if you could enlighten me :)

Many thanks again,

Ben



> On 26 Aug 2016, at 14:28, Ben RUBSON <ben.rubson at gmail.com> wrote:
> 
> Yes Juergen, metadata only stores in ARC files' info (location in pool and some other useful info), not the user data.
> 
> I think "find" only needs metadata, as it does not read the files' content.
> Which can be "verified" because :
> - there is no IO at all on the pool (after the first find loop, once ARC has the needed metadata) ;
> - there is no ARC demand data at all.
> But I may be wrong, so of course feel free to correct me. Thank you.
> 
> Thank you for the links, I already read them before posting here, but I may have missed something.
> 
> Ben
> 
>> On 26 Aug 2016, at 14:16, InterNetX - Juergen Gotteswinter <juergen.gotteswinter at internetx.com> wrote:
>> 
>> so, you know the difference between
>> 
>> - metadata
>> - data
>> 
>> ?
>> 
>> if yes, what is your find actually doing in this case?
>> 
>> regarding arc
>> 
>> http://dtrace.org/blogs/brendan/2012/01/09/activity-of-the-zfs-arc/
>> https://www.patpro.net/blog/index.php/2014/03/19/2628-zfs-primarycache-all-versus-metadata/
>> 
>> 
>> 
>> Am 26.08.2016 um 14:06 schrieb Ben RUBSON:
>>> Juergen, thank you for your answer.
>>> So where do you think these ARC misses come from ? I can't find out :S
>>> Thank you !
>>> 
>>>> On 26 Aug 2016, at 14:01, InterNetX - Juergen Gotteswinter <juergen.gotteswinter at internetx.com> wrote:
>>>> 
>>>> no bug, everything like i whould expect
>>>> 
>>>> Am 26.08.2016 um 11:40 schrieb Ben RUBSON:
>>>>> uname -v
>>>>> FreeBSD 11.0-RC2 #0 r304729: Wed Aug 24 06:59:03 UTC 2016 root at releng2.nyi.freebsd.org:/usr/obj/usr/src/sys/GENERIC