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Reply-To: user@ignite.apache.org
Date: Thu, 10 Aug 2017 08:59:32 +0000 (UTC)
From: Alexey Kukushkin <alexeykukushkin@yahoo.com>
Reply-To: Alexey Kukushkin <alexeykukushkin@yahoo.com>
To: <user@ignite.apache.org>
Message-ID: <1534133721.986140.1502355572149@mail.yahoo.com>
In-Reply-To: <1502332715718-16092.post@n6.nabble.com>
References: <1502332715718-16092.post@n6.nabble.com>
Subject: Re: Persistent store and eviction policy.
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Hi,
1. Persistence and Data Eviction are alternative options to handle out-of-m=
emory scenarios.Persistence makes Ignite fill all available RAM and move th=
e oldest page to the =E2=80=9Cdisk=E2=80=9D part of the cache when there is=
 not enough memory.
Data eviction policy makes Ignite to completely remove some entries or memo=
ry pages from the cache depending on the policy.Persistence comes at cost o=
f performance but gives us virtually unlimited reliable cache.Use the one o=
r the other.

2. No, if you have no backups configured and a node goes down the data beco=
mes unavailable. Persistence will not help - only partitions that a nodes o=
wns are persisted on the node. Configure backups to address the issue.
Best regards,=C2=A0Alexey


On Thursday, August 10, 2017, 5:38:50 AM GMT+3, userx <gagansab@gmail.com> =
wrote:

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 ho=
t
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 persisten=
t
store is enabled.=20

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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<html><head></head><body><div style=3D"font-family:Helvetica Neue, Helvetic=
a, Arial, sans-serif;font-size:small;"><div><div>Hi,</div><div><br></div><d=
iv>1. Persistence and Data Eviction are alternative options to handle out-o=
f-memory scenarios.</div>Persistence makes Ignite fill all available RAM an=
d move the oldest page to the =E2=80=9Cdisk=E2=80=9D part of the cache when=
 there is not enough memory.<br>Data eviction policy makes Ignite to comple=
tely remove some entries or memory pages from the cache depending on the po=
licy.</div><div>Persistence comes at cost of performance but gives us virtu=
ally unlimited reliable cache.</div><div>Use the one or the other.<br><div>=
<br></div><div>2. No, if you have no backups configured and a node goes dow=
n the data becomes unavailable. Persistence will not help - only partitions=
 that a nodes owns are persisted on the node. Configure backups to address =
the issue.</div><div><br></div><div class=3D"ydp6a1a130csignature">Best reg=
ards,&nbsp;<div>Alexey</div></div><div><br></div></div><div><br></div><div>=
<br></div><div id=3D"yahoo_quoted_3060599634" class=3D"yahoo_quoted"><div s=
tyle=3D"font-family:'Helvetica Neue', Helvetica, Arial, sans-serif;font-siz=
e:13px;color:#26282a;"><div>On Thursday, August 10, 2017, 5:38:50 AM GMT+3,=
 userx &lt;gagansab@gmail.com&gt; wrote:</div><div><br></div><div><br></div=
><div><div dir=3D'ltr'>Hi team,<br></div><div dir=3D'ltr'><br></div><div di=
r=3D'ltr'>I was going through the documentation of durable memory at<br></d=
iv><div dir=3D'ltr'><a href=3D"https://apacheignite.readme.io/docs/durable-=
memory" target=3D_blank>https://apacheignite.readme.io/docs/durable-memory<=
/a><br></div><div dir=3D'ltr'><br></div><div dir=3D'ltr'>As per the documen=
tation, durable memory comes into picture when<br></div><div dir=3D'ltr'>Pe=
rsistentStore configuration is enabled. Now durable memory uses both<br></d=
iv><div dir=3D'ltr'>RAM(hot data) and disk (superset). When the RAM part re=
aches a threshold<br></div><div dir=3D'ltr'>(80% by default as per the docu=
mentation), the durable data retains only hot<br></div><div dir=3D'ltr'>dat=
a in RAM and rest on the disk.<br></div><div dir=3D'ltr'><br></div><div dir=
=3D'ltr'>QUESTION 1<br></div><div dir=3D'ltr'>So does that mean that there =
is a default eviction policy which comes into<br></div><div dir=3D'ltr'>exi=
stence ? Or does the user explicitly has to mention the same in<br></div><d=
iv dir=3D'ltr'>configuration ? What happens if he does not mention the evic=
tion policy in<br></div><div dir=3D'ltr'>configuration ?<br></div><div dir=
=3D'ltr'><br></div><div dir=3D'ltr'>Suppose there are 2 nodes N1 (different=
 physical box) and N2 (different<br></div><div dir=3D'ltr'>physical box) an=
d the data is distributed in PARTITIONED mode and persistent<br></div><div =
dir=3D'ltr'>store is enabled. <br></div><div dir=3D'ltr'><br></div><div dir=
=3D'ltr'>Here is the example of entries<br></div><div dir=3D'ltr'><br></div=
><div dir=3D'ltr'>N1-&gt; "1","X"<br></div><div dir=3D'ltr'>N2-&gt; "2","Y"=
<br></div><div dir=3D'ltr'><br></div><div dir=3D'ltr'>QUESTION 2<br></div><=
div dir=3D'ltr'>Suppose N1 crashes and goes down and does not come up at al=
l for say 5<br></div><div dir=3D'ltr'>hours. Is "1" retrievable at all duri=
ng that time if N1 went down after an<br></div><div dir=3D'ltr'>entry to it=
s WAL file or we loose N1 ? If say the entry was not able to be<br></div><d=
iv dir=3D'ltr'>made in WAL file and should we have configured a back up as =
N3 (different<br></div><div dir=3D'ltr'>physical box), would it have saved =
"1" ?<br></div><div dir=3D'ltr'><br></div><div dir=3D'ltr'><br></div><div d=
ir=3D'ltr'><br></div><div dir=3D'ltr'><br></div><div dir=3D'ltr'><br></div>=
<div dir=3D'ltr'><br></div><div dir=3D'ltr'><br></div><div dir=3D'ltr'>--<b=
r></div><div dir=3D'ltr'>View this message in context: <a href=3D"http://ap=
ache-ignite-users.70518.x6.nabble.com/Persistent-store-and-eviction-policy-=
tp16092.html" target=3D_blank>http://apache-ignite-users.70518.x6.nabble.co=
m/Persistent-store-and-eviction-policy-tp16092.html</a><br></div><div dir=
=3D'ltr'>Sent from the Apache Ignite Users mailing list archive at Nabble.c=
om.<br></div></div></div></div></div></body></html>
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