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Posted to issues@ignite.apache.org by "Denis Magda (Jira)" <ji...@apache.org> on 2019/09/13 16:40:00 UTC
[jira] [Commented] (IGNITE-10862) Introduce tool to free up space
on a disc of unused memory pages
[ https://issues.apache.org/jira/browse/IGNITE-10862?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16929354#comment-16929354 ]
Denis Magda commented on IGNITE-10862:
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[~agoncharuk] is this a fundamental problem in our architecture? If not to know all the details it sounds like each node needs to spawn a background thread that will be cleaning disk space.
> Introduce tool to free up space on a disc of unused memory pages
> ----------------------------------------------------------------
>
> Key: IGNITE-10862
> URL: https://issues.apache.org/jira/browse/IGNITE-10862
> Project: Ignite
> Issue Type: Improvement
> Components: persistence
> Affects Versions: 2.7
> Reporter: Vyacheslav Daradur
> Priority: Critical
> Fix For: 2.8
>
>
> At the current time, Ignite is not able to release occupied disc space even if a significant amount of data was removed from IgniteCache. It disturbs our users because they can't use hardware effectively, also it increases TCO.
> *Use-cases:*
> 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;
> *Possible solutions:*
> Introduce some kind of mechanics which will be able to shrink data in IgniteCache and to free up space on a disc of mapped free memory pages.
> A solution should take into account possible concurrent reads and updates of data and indexes to maintain consistency.
> Maybe, it makes sense to implement a tool to be offline at the first step that means concurrent operations will be prohibited.
> Strongly recommended discussing design on dev-list with Ignite experts before the start of implementation.
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