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From Valentin Kulichenko <valentin.kuliche...@gmail.com>
Subject Re: Eviction policies with persistence
Date Thu, 01 Feb 2018 19:23:55 GMT
Guys,

Thanks for responses. But I still fail to understand how it affects a user.

Are you saying that with persistence enabled Random-LRU is always used
regardless of what is specified in pageEvictionMode, while in in-memory
only scenario we can also utilize Random-2-LRU for eviction? Is this
accurate? Are there any other differences?

-Val

On Thu, Feb 1, 2018 at 5:01 AM, Dmitry Pavlov <dpavlov.spb@gmail.com> wrote:

> 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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