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From John Wilson <sami.hailu...@gmail.com>
Subject Re: Quick questions on Evictions
Date Mon, 04 Sep 2017 18:33:22 GMT
I appreciate the nice explanation. I got a few more questions:


   1. For the case where on-heap caching and persistent are both disabled,
   why does Ignite throw out out-dated pages from off-heap? Why not throw OOM
   error since the out-dated pages are not backed by persistent store and
   throwing away results in data loss?
   2. For off-heap eviction with persistent store enabled, will entries
   evicted from data pages be written to disk (in case they are dirty) or will
   they be thrown away (which would imply that entries eligible for eviction
   must be clean and have already been written to disk by checkpointing)?
   3.  Checkpointing works by locating dirty pages and writing them out. If
   a single entry in a data page is dirty (has been updated since the last
   check pointing), will checkpointing write the entire data page (all
   entries) to the partition files or just the dirty entry?

Thanks!

On Mon, Sep 4, 2017 at 8:17 AM, dkarachentsev <dkarachentsev@gridgain.com>
wrote:

> Hi,
>
> Assume you have disabled onheapCahe and disabled persistence. In that case
> you may configure only datapage eviction mode, then outdated pages will be
> thrown away, when no free memory will be available for Ignite. Also you
> cannot configure per-entry eviction.
>
> OK, if you enable onheapCache, then Ignite will store on heap every entry
> that was read from off-heap (or disk). Next reads of it will not require
> off-heap readings, and every update will write to off-heap. To limit size
> of
> onheapCache you may set CacheConfiguration.setEvictionPolicy(), but it
> will
> not evict off-heap entries.
>
> So, off-heap eviction may be controlled with DataPageEvictionMode only, and
> as you suggested, it clears entries one-by-one from page, checking for
> current locks (transaction locks as well). If entry is locked, it won't be
> evicted.
>
> Thanks!
> -Dmitry.
>
>
>
> --
> Sent from: http://apache-ignite-users.70518.x6.nabble.com/
>

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