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From pstanh...@wimba.com
Subject Re: Seeds, autobootstrap nodes, and replication factor
Date Sat, 05 Jun 2010 01:51:05 GMT
I never said it would be frequent. That was an assumption made by Ben. 

I am trying to understand how to "set the dials" to ensure availability and durability ...
And understand the cost when the inevitable hardware failure occurs. 


Sent via BlackBerry from T-Mobile

-----Original Message-----
From: Jonathan Shook <jshook@gmail.com>
Date: Fri, 4 Jun 2010 20:28:33 
To: <user@cassandra.apache.org>
Subject: Re: Seeds, autobootstrap nodes, and replication factor

If I may ask, why the need for frequent topology changes?


On Fri, Jun 4, 2010 at 1:21 PM, Benjamin Black <b@b3k.us> wrote:
> On Fri, Jun 4, 2010 at 11:14 AM, Philip Stanhope <pstanhope@wimba.com> wrote:
>> I guess I'm thick ...
>>
>> What would be the right choice? Our data demands have already been proven to scale
beyond what RDB can handle for our purposes. We are quite pleased with Cassandra read/write/scale
out. Just trying to understand the operational considerations.
>>
>
> Cassandra supports online topology changes, but those operations are
> not cheap.  If you are expecting frequent addition and removal of
> nodes from a ring, things will be very unstable or slow (or both).  As
> I already mentioned, having a large cluster (and 40 nodes qualifies
> right now) with RF=number of nodes is going to make read and write
> operations get more and more expensive as the cluster grows.  While
> you might see reasonable performance at current, small scale, it will
> not be the case when the cluster gets large.
>
> I am not aware of anything like Cassandra (or any other Dynamo system)
> that support such extensive replication and topology churn.  You might
> have to write it.
>
>
> b
>
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