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From Denis Magda <dma...@apache.org>
Subject Re: How to free up space on disc after removing entries from IgniteCache with enabled PDS?
Date Fri, 28 Dec 2018 17:45:10 GMT
Shouldn't the OS care of defragmentation? What we need to do is to give a
way to remove stale data and "release" the allocated space somehow through
the tools, MBeans or API methods.

--
Denis


On Fri, Dec 28, 2018 at 6:24 AM Vladimir Ozerov <vozerov@gridgain.com>
wrote:

> Hi Vyacheslav,
>
> AFAIK this is not implemented. Shrinking/defragmentation is important
> optimization. Not only because it releases free space, but also because it
> decreases total number of pages. But is it not very easy to implement, as
> you have to both reshuffle data entries and index entries, maintaining
> consistency for concurrent reads and updates at the same time. Or
> alternatively we can think of offline defragmentation. It will be easier to
> implement and faster, but concurrent operations will be prohibited.
>
> On Fri, Dec 28, 2018 at 4:08 PM Vyacheslav Daradur <daradurvs@gmail.com>
> wrote:
>
> > Igniters, we have faced with the following problem on one of our
> > deployments.
> >
> > Let's imagine that we have used IgniteCache with enabled PDS during the
> > time:
> > - hardware disc space has been occupied during growing up of an amount
> > of data, e.g. 100Gb;
> > - then, we removed non-actual data, e.g 50Gb, which became useless for
> us;
> > - disc space stopped growing up with new data, but it was not
> > released, and still took 100Gb, instead of expected 50Gb;
> >
> > Another use case:
> > - a user extracts data from IgniteCache to store it in separate
> > IgniteCache or another store;
> > - disc still is occupied and the user is not able to store data in the
> > different cache at the same cluster because of disc limitation;
> >
> > How can we help the user to free up the disc space, if an amount of
> > data in IgniteCache has been reduced many times and will not be
> > increased in the nearest future?
> >
> > AFAIK, we have mechanics of reusing memory pages, that allows us to
> > use pages which have been allocated and stored removed data for
> > storing new data.
> > Are there any chances to shrink data and free up space on disc (with
> > defragmentation if possible)?
> >
> > --
> > Best Regards, Vyacheslav D.
> >
>

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