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Message-ID: 
 <CALwhUOWPQC2gJk=LGyVXD6jVPJ9Scc9Pe4a38VH=rA_LYX6ACw@mail.gmail.com>
Subject: Vnodes and replication
To: user@cassandra.apache.org
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After reading through the vnodes and partitioning described in the datastax
documentation, I am still confused about how rows are
partitioned/replicated.

With vnodes, I know that each Node on the ring now supports many token
ranges per Node. However I am still not very clear on how the replication
is carried out.

If I have 4 Nodes A, B, C, D and their ranges are below.

A - [1,2,3,4]
B - [5,6,7,8]
C - [9,10,11,12]
D - [13,14,15,16]

After a shuffle, lets assume the Nodes are shuffled like this.

A - [1,5,13,9]
B - [2,6,14,10]
C - [3,7,15,11]
D - [4,8,16,12]

now if I use a simple replication strategy and RF=3, the first replica
rowkey gets placed on node determined by the partitioner.

Prior to vnode, if my rowkey hash is 2, it gets placed on Nodes A, B, C.
With the above vnode setup, if my rowkey hash is 2, does it get placed in
B, C, D ?

cheers!

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Content-Type: text/html; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable

<div dir=3D"ltr"><p style=3D"margin:0px 0px 1em;padding:0px;border:0px;font=
-size:14px;vertical-align:baseline;clear:both;color:rgb(0,0,0);font-family:=
Arial,&#39;Liberation Sans&#39;,&#39;DejaVu Sans&#39;,sans-serif;line-heigh=
t:17.804800033569336px">

After reading through the vnodes and partitioning described in the datastax=
 documentation, I am still confused about how rows are partitioned/replicat=
ed.</p><p style=3D"margin:0px 0px 1em;padding:0px;border:0px;font-size:14px=
;vertical-align:baseline;clear:both;color:rgb(0,0,0);font-family:Arial,&#39=
;Liberation Sans&#39;,&#39;DejaVu Sans&#39;,sans-serif;line-height:17.80480=
0033569336px">

With vnodes, I know that each Node on the ring now supports many token rang=
es per Node. However I am still not very clear on how the replication is ca=
rried out.</p><p style=3D"margin:0px 0px 1em;padding:0px;border:0px;font-si=
ze:14px;vertical-align:baseline;clear:both;color:rgb(0,0,0);font-family:Ari=
al,&#39;Liberation Sans&#39;,&#39;DejaVu Sans&#39;,sans-serif;line-height:1=
7.804800033569336px">

If I have 4 Nodes A, B, C, D and their ranges are below.</p><pre style=3D"m=
argin-top:0px;margin-bottom:10px;padding:5px;border:0px;font-size:14px;vert=
ical-align:baseline;background-color:rgb(238,238,238);font-family:Consolas,=
Menlo,Monaco,&#39;Lucida Console&#39;,&#39;Liberation Mono&#39;,&#39;DejaVu=
 Sans Mono&#39;,&#39;Bitstream Vera Sans Mono&#39;,&#39;Courier New&#39;,mo=
nospace,serif;overflow:auto;width:auto;max-height:600px;word-wrap:normal;co=
lor:rgb(0,0,0);line-height:17.804800033569336px">

<code style=3D"margin:0px;padding:0px;border:0px;vertical-align:baseline;fo=
nt-family:Consolas,Menlo,Monaco,&#39;Lucida Console&#39;,&#39;Liberation Mo=
no&#39;,&#39;DejaVu Sans Mono&#39;,&#39;Bitstream Vera Sans Mono&#39;,&#39;=
Courier New&#39;,monospace,serif;white-space:inherit">A - [1,2,3,4]
B - [5,6,7,8]
C - [9,10,11,12]
D - [13,14,15,16] =20
</code></pre><p style=3D"margin:0px 0px 1em;padding:0px;border:0px;font-siz=
e:14px;vertical-align:baseline;clear:both;color:rgb(0,0,0);font-family:Aria=
l,&#39;Liberation Sans&#39;,&#39;DejaVu Sans&#39;,sans-serif;line-height:17=
.804800033569336px">

After a shuffle, lets assume the Nodes are shuffled like this.</p><pre styl=
e=3D"margin-top:0px;margin-bottom:10px;padding:5px;border:0px;font-size:14p=
x;vertical-align:baseline;background-color:rgb(238,238,238);font-family:Con=
solas,Menlo,Monaco,&#39;Lucida Console&#39;,&#39;Liberation Mono&#39;,&#39;=
DejaVu Sans Mono&#39;,&#39;Bitstream Vera Sans Mono&#39;,&#39;Courier New&#=
39;,monospace,serif;overflow:auto;width:auto;max-height:600px;word-wrap:nor=
mal;color:rgb(0,0,0);line-height:17.804800033569336px">

<code style=3D"margin:0px;padding:0px;border:0px;vertical-align:baseline;fo=
nt-family:Consolas,Menlo,Monaco,&#39;Lucida Console&#39;,&#39;Liberation Mo=
no&#39;,&#39;DejaVu Sans Mono&#39;,&#39;Bitstream Vera Sans Mono&#39;,&#39;=
Courier New&#39;,monospace,serif;white-space:inherit">A - [1,5,13,9]
B - [2,6,14,10]
C - [3,7,15,11]
D - [4,8,16,12]
</code></pre><p style=3D"margin:0px 0px 1em;padding:0px;border:0px;font-siz=
e:14px;vertical-align:baseline;clear:both;color:rgb(0,0,0);font-family:Aria=
l,&#39;Liberation Sans&#39;,&#39;DejaVu Sans&#39;,sans-serif;line-height:17=
.804800033569336px">

now if I use a simple replication strategy and=A0<code style=3D"margin:0px;=
padding:1px 5px;border:0px;vertical-align:baseline;background-color:rgb(238=
,238,238);font-family:Consolas,Menlo,Monaco,&#39;Lucida Console&#39;,&#39;L=
iberation Mono&#39;,&#39;DejaVu Sans Mono&#39;,&#39;Bitstream Vera Sans Mon=
o&#39;,&#39;Courier New&#39;,monospace,serif;white-space:pre-wrap">RF=3D3</=
code>, the first replica rowkey gets placed on node determined by the parti=
tioner.</p>

<p style=3D"margin:0px 0px 1em;padding:0px;border:0px;font-size:14px;vertic=
al-align:baseline;clear:both;color:rgb(0,0,0);font-family:Arial,&#39;Libera=
tion Sans&#39;,&#39;DejaVu Sans&#39;,sans-serif;line-height:17.804800033569=
336px">

Prior to vnode, if my rowkey hash is 2, it gets placed on Nodes A, B, C. Wi=
th the above vnode setup, if my rowkey hash is 2, does it get placed in B, =
C, D ?</p><p style=3D"margin:0px 0px 1em;padding:0px;border:0px;font-size:1=
4px;vertical-align:baseline;clear:both;color:rgb(0,0,0);font-family:Arial,&=
#39;Liberation Sans&#39;,&#39;DejaVu Sans&#39;,sans-serif;line-height:17.80=
4800033569336px">

cheers!</p></div>

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