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From Dmitry Pavlov <dpavlov....@gmail.com>
Subject Re: Eviction policies with persistence
Date Thu, 01 Feb 2018 13:01:29 GMT
Hi Vyacheslav,

Yes, this is right, but for now PDS page based eviction uses Random-LRU,
not Random-2-LRU. Something may be changed in future Ignite releases, but
now Random-LRU is used. I am going to research if there is some room for
improvements in this aspect (e.g. IGNITE-7507 recenly found).

If clean page is evicted, nothing really happends. If dirty page is evicted
from region during checkpointing process run, page is stored in file before
eviction

Some info about this can be found in
https://cwiki.apache.org/confluence/display/IGNITE/Ignite+Durable+Memory+-+under+the+hood#IgniteDurableMemory-underthehood-Pagebasedeviction

Sincerely,
Dmitriy Pavlov

чт, 1 февр. 2018 г. в 9:53, Vyacheslav Daradur <daradurvs@gmail.com>:

> Hi Valentin,
>
> As far as I know, when persistence is enabled and Ignite can't
> allocate new page-memory in the memory segment, then Ignite
> automatically evict some data from RAM to PDS using Random-2-LRU
> eviction algorithm. And there are no mechanisms to evict entries out
> when PDS is enabled.
>
> I'll be glad if I am not right and someone will correct me because, as
> Ignite user, I can't use PDS only as RAM disk replication for the use
> case in my project.
>
>
> On Thu, Feb 1, 2018 at 3:53 AM, Valentin Kulichenko
> <valentin.kulichenko@gmail.com> wrote:
> > Folks,
> >
> > On "Eviction Policies" documentation page [1] we have the following
> callout:
> >
> >> Configured eviction policy has no effect if Ignite persistence is
> enabled
> >> Note that if Ignite Persistence is enabled, then the page-based
> evictions
> > have no effect because the oldest pages will be purged from memory
> > automatically.
> >
> > This really confuses me. Why is there a difference in how data is evicted
> > from memory depending on having disk enabled or not? And how does
> eviction
> > work with persistence enabled then?
> >
> > Does anyone can clarify?
> >
> > [1] https://apacheignite.readme.io/docs/evictions
> >
> > -Val
>
>
>
> --
> Best Regards, Vyacheslav D.
>

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