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From: Oleg Tsvinev <oleg.tsvinev@gmail.com>
Date: Wed, 17 Aug 2011 07:58:24 -0700
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 <CAOg3g-xFktbTtDseQ789QY=kgcfXejtN8u-LdDB7yM7ZHaHScA@mail.gmail.com>
Subject: Re: Cassandra in Multiple Datacenters Active - Standby configuration
To: user@cassandra.apache.org
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Aaron,

Can you point to a line in Cassandra sources where you believe it does
not understand the "multi ring" approach?
I'm not sure about Cassandra team but Hector team likes pull requests
with patches.
Anyways, I believe I should run a test to see if data is indeed
replicated between datacenters.

And I voted on the issue.

On Wed, Aug 17, 2011 at 2:20 AM, aaron morton <aaron@thelastpickle.com> wro=
te:
>
> The calculation for ownership does not understand the "multi ring" approa=
ch to assigning tokens. I've created=C2=A0https://issues.apache.org/jira/br=
owse/CASSANDRA-3047=C2=A0for you.
> Otherwise your tokens look good to me.
> Cheers
> -----------------
> Aaron Morton
> Freelance Cassandra Developer
> @aaronmorton
> http://www.thelastpickle.com
> On 17/08/2011, at 9:19 AM, Oleg Tsvinev wrote:
>
> Hi all,
>
> I followed instructions here:
> http://wiki.apache.org/cassandra/Operations#Token_selection
> to create a Cassandra cluster spanning two datacenters. Now I see that
> nodes belonging to DC2 datacenter own 0% of the ring. I would expect
> them to own 50%.
>
> Does anyone have an idea what's going on here?
>
> root@casper02:~# nodetool -h 10.4.64.63 ring
> Address =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0DC =C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0Rack =C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0Status State =C2=A0=C2=A0Load
> Owns =C2=A0=C2=A0=C2=A0Token
>
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A08507059173023461586584365185794=
2052865
> 10.4.64.63 =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0DC1 =C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0RAC1 =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0Up =C2=
=A0=C2=A0=C2=A0=C2=A0Normal =C2=A036.19 MB
> 50.00% =C2=A00
> 10.4.65.55 =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0DC2 =C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0RAC1 =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0Up =C2=
=A0=C2=A0=C2=A0=C2=A0Normal =C2=A036.21 MB
> 0.00% =C2=A0=C2=A01
> 10.4.65.73 =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0DC1 =C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0RAC1 =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0Up =C2=
=A0=C2=A0=C2=A0=C2=A0Normal =C2=A0530.12 KB
> 50.00% =C2=A085070591730234615865843651857942052864
> 10.4.64.166 =C2=A0=C2=A0=C2=A0=C2=A0DC2 =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0RAC1 =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0Up =C2=A0=C2=
=A0=C2=A0=C2=A0Normal =C2=A0525.68 KB
> 0.00% =C2=A0=C2=A085070591730234615865843651857942052865
>
> Thank you,
> =C2=A0Oleg
>
> -------------
>
> On Mon, Aug 15, 2011 at 1:39 PM, Oleg Tsvinev <oleg.tsvinev@gmail.com> wr=
ote:
>
> Hi all,
>
> I have a question that documentation=C2=A0has not clear answer for. I hav=
e
>
> the following requirements:
>
> 1. Synchronously store data in datacenter DC1 on 2+ nodes
>
> 2. Asynchronously replicate the same data to DC2 and store it on 2+
>
> nodes to act as a hot standby
>
> Now, I have configured keyspaces with o.a.c.l.NetworkTopologyStrategy
>
> with strategy_options=3D[{DC1:2, DC2:2}] and use LOCAL_QUORUM
>
> consistency level, following documentation here:
>
> http://www.datastax.com/docs/0.8/operations/datacenter
>
> Now, how do I assign initial tokens? If I have, say 6 nodes total, 3
>
> in DC1 and 3 in DC2, and create a ring as if all 6 nodes share the
>
> total 2^128 space equally.
>
> Now say node N1:DC2 has key K and is in remote datacenter (for an app
>
> in DC1). Wouldn't Cassandra always forward K to the DC2 node N1 thus
>
> turning asynchronous writes into synchronous ones? Performance impact
>
> will be huge as the latency between DC1 and DC2 is significant.
>
> I hope there's an answer and I'm just missing something. My case falls
>
> under Disaster Recovery in
>
> http://www.datastax.com/docs/0.8/operations/datacenter but I don't see
>
> how Cassandra will support my use case.
>
> I appreciate any help on this.
>
> Thank you,
>
> =C2=A0Oleg
>
>