cassandra-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Oleg Tsvinev <oleg.tsvi...@gmail.com>
Subject Re: Cassandra in Multiple Datacenters Active - Standby configuration
Date Tue, 16 Aug 2011 21:19:21 GMT
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         DC          Rack        Status State   Load
Owns    Token

        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

Thank you,
  Oleg

-------------

On Mon, Aug 15, 2011 at 1:39 PM, Oleg Tsvinev <oleg.tsvinev@gmail.com> wrote:
> Hi all,
>
> I have a question that documentation has not clear answer for. I have
> 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=[{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,
>  Oleg
>

Mime
View raw message