[ZFS] ARC accounting bug ?

[Ben RUBSON]

Linda,
Thank you very much for your suggestion.
However atime is off on my pool.


> On 26 Aug 2016, at 17:46, Linda Kateley <lkateley at kateley.com> wrote:
> 
> Metadata updates when you access a file. Atime is most often updated and you will miss.
> 
> If you are running vm's on zfs I always recommend to turn off atime updates.
> 
> Metadata is usually tiny so you probably won't see disk activity
> 
> 
> On 8/26/16 10:27 AM, Ben RUBSON wrote:
>> 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
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