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Subject: Re: Cassandra in Multiple Datacenters Active - Standby configuration
From: aaron morton <aaron@thelastpickle.com>
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Date: Thu, 18 Aug 2011 10:49:58 +1200
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To: user@cassandra.apache.org

See the bug report, implementations of IPartitioner.describeOwnership()

Cheers

-----------------
Aaron Morton
Freelance Cassandra Developer
@aaronmorton
http://www.thelastpickle.com

On 18/08/2011, at 2:58 AM, Oleg Tsvinev wrote:

> Aaron,
>=20
> 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.
>=20
> And I voted on the issue.
>=20
> On Wed, Aug 17, 2011 at 2:20 AM, aaron morton =
<aaron@thelastpickle.com> wrote:
>>=20
>> The calculation for ownership does not understand the "multi ring" =
approach to assigning tokens. I've created =
https://issues.apache.org/jira/browse/CASSANDRA-3047 for 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:
>>=20
>> Hi all,
>>=20
>> 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%.
>>=20
>> Does anyone have an idea what's going on here?
>>=20
>> root@casper02:~# nodetool -h 10.4.64.63 ring
>> Address         DC          Rack        Status State   Load
>> Owns    Token
>>=20
>>        85070591730234615865843651857942052865
>> 10.4.64.63      DC1         RAC1        Up     Normal  36.19 MB
>> 50.00%  0
>> 10.4.65.55      DC2         RAC1        Up     Normal  36.21 MB
>> 0.00%   1
>> 10.4.65.73      DC1         RAC1        Up     Normal  530.12 KB
>> 50.00%  85070591730234615865843651857942052864
>> 10.4.64.166     DC2         RAC1        Up     Normal  525.68 KB
>> 0.00%   85070591730234615865843651857942052865
>>=20
>> Thank you,
>>  Oleg
>>=20
>> -------------
>>=20
>> On Mon, Aug 15, 2011 at 1:39 PM, Oleg Tsvinev =
<oleg.tsvinev@gmail.com> wrote:
>>=20
>> Hi all,
>>=20
>> I have a question that documentation has not clear answer for. I have
>>=20
>> the following requirements:
>>=20
>> 1. Synchronously store data in datacenter DC1 on 2+ nodes
>>=20
>> 2. Asynchronously replicate the same data to DC2 and store it on 2+
>>=20
>> nodes to act as a hot standby
>>=20
>> Now, I have configured keyspaces with o.a.c.l.NetworkTopologyStrategy
>>=20
>> with strategy_options=3D[{DC1:2, DC2:2}] and use LOCAL_QUORUM
>>=20
>> consistency level, following documentation here:
>>=20
>> http://www.datastax.com/docs/0.8/operations/datacenter
>>=20
>> Now, how do I assign initial tokens? If I have, say 6 nodes total, 3
>>=20
>> in DC1 and 3 in DC2, and create a ring as if all 6 nodes share the
>>=20
>> total 2^128 space equally.
>>=20
>> Now say node N1:DC2 has key K and is in remote datacenter (for an app
>>=20
>> in DC1). Wouldn't Cassandra always forward K to the DC2 node N1 thus
>>=20
>> turning asynchronous writes into synchronous ones? Performance impact
>>=20
>> will be huge as the latency between DC1 and DC2 is significant.
>>=20
>> I hope there's an answer and I'm just missing something. My case =
falls
>>=20
>> under Disaster Recovery in
>>=20
>> http://www.datastax.com/docs/0.8/operations/datacenter but I don't =
see
>>=20
>> how Cassandra will support my use case.
>>=20
>> I appreciate any help on this.
>>=20
>> Thank you,
>>=20
>>  Oleg
>>=20
>>=20