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From: Mark Greene <greenemj@gmail.com>
Date: Tue, 11 May 2010 14:31:27 -0400
Message-ID: <AANLkTiljQkUMp2uoGcXFbP-zHhRNoVKetExiNVTlpYxV@mail.gmail.com>
Subject: Re: replication impact on write throughput
To: user@cassandra.apache.org
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If you have for example, your replication factor equal to the total amount
of nodes in the ring, I suspect you will hit a brick wall pretty soon.

The biggest impact on your write performance will most likely be the
consistency level of your writes. In other words, how many nodes you want to
wait for before you acknowledge the write back to the client.


On Tue, May 11, 2010 at 12:10 PM, Bill de hOra <bill@dehora.net> wrote:

> If I had 10 Cassandra nodes each with a write capacity of 5K per second and
> a replication factor of 2, would that mean the expected write capacity of
> the system would be ~25K writes per second because the nodes are also
> serving other nodes and not just clients?
>
> I know this is highly simplified take on things (ie no consideration for
> reads or quorum), I'm just trying to understand what the implication of
> replication is on write scalability. Intuitively it would seem actual write
> capacity is total write capacity divided by the replication factor.
>
> Bill
>

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If you have for example, your replication factor equal to the total amount =
of nodes in the ring, I suspect you will hit a brick wall pretty soon.<div>=
<br></div><div>The biggest impact on your write performance will most likel=
y be the consistency level of your writes. In other words, how many nodes y=
ou want to wait for before you acknowledge the write back to the client.</d=
iv>

<div><br></div><div><br><br><div class=3D"gmail_quote">On Tue, May 11, 2010=
 at 12:10 PM, Bill de hOra <span dir=3D"ltr">&lt;<a href=3D"mailto:bill@deh=
ora.net">bill@dehora.net</a>&gt;</span> wrote:<br><blockquote class=3D"gmai=
l_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left=
:1ex;">

If I had 10 Cassandra nodes each with a write capacity of 5K per second and=
 a replication factor of 2, would that mean the expected write capacity of =
the system would be ~25K writes per second because the nodes are also servi=
ng other nodes and not just clients?<br>


<br>
I know this is highly simplified take on things (ie no consideration for re=
ads or quorum), I&#39;m just trying to understand what the implication of r=
eplication is on write scalability. Intuitively it would seem actual write =
capacity is total write capacity divided by the replication factor.<br>

<font color=3D"#888888">
<br>
Bill<br>
</font></blockquote></div><br></div>

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