Vyacheslav Daradur created IGNITE-10862:
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Summary: 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
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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