zfs performance degradation

[Dmitrijs]

2015.09.23. 23:08, Paul Kraus пишет:
> On Sep 22, 2015, at 13:38, Dmitrijs <war at dim.lv> wrote:
>
>>   I've encountered strange ZFS behavior - serious performance degradation over few days.
>>
>> Could it happen because of pool being 78% full? So I cannot fill puls full?
>> Can anyone please advice how could I fix the situation - or is it normal?
>
> So the short answer (way too late for that) is that you can, in fact, not use all of the capacity of a zpool unless the data is written once, never modified, and you do not have any snapshots, clones, or the like.
>
> P.S. I assume you are not using DeDupe ? You do not have anywhere enough RAM for that.
>
> --
> Paul Kraus
> paul at kraus-haus.org
>
Thank you very much for explanation. Am I getting it right - it will not 
work faster even if I add +4Gb RAM to be 8Gb in total? I am not using 
DeDuplication and compression, neither planing using them.

I've also put down a lot of research for situation here: 
http://forums.nas4free.org/viewtopic.php?f=66&t=9595
In short: you are right, everything getting slowly when pool fills up.


So if I plan to work with data a lot, get decent performance and still 
be sure I'm on the safe side with mirror-raid1, should I choose another 
filesystem? Especially, if i do not really need snapshots, clones, etc.
Or is it not possible at all, and I should put something like raid0 for 
work and tolerate slow backup on raid1 at nights?


best regards,
Dmitriy