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From userx <gagan...@gmail.com>
Subject Persistent store and eviction policy.
Date Thu, 10 Aug 2017 02:38:35 GMT
Hi team,

I was going through the documentation of durable memory at
https://apacheignite.readme.io/docs/durable-memory

As per the documentation, durable memory comes into picture when
PersistentStore configuration is enabled. Now durable memory uses both
RAM(hot data) and disk (superset). When the RAM part reaches a threshold
(80% by default as per the documentation), the durable data retains only hot
data in RAM and rest on the disk.

QUESTION 1
So does that mean that there is a default eviction policy which comes into
existence ? Or does the user explicitly has to mention the same in
configuration ? What happens if he does not mention the eviction policy in
configuration ?

Suppose there are 2 nodes N1 (different physical box) and N2 (different
physical box) and the data is distributed in PARTITIONED mode and persistent
store is enabled. 

Here is the example of entries

N1-> "1","X"
N2-> "2","Y"

QUESTION 2
Suppose N1 crashes and goes down and does not come up at all for say 5
hours. Is "1" retrievable at all during that time if N1 went down after an
entry to its WAL file or we loose N1 ? If say the entry was not able to be
made in WAL file and should we have configured a back up as N3 (different
physical box), would it have saved "1" ?







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