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Ananth Gundabattula commented on CASSANDRA-5684:
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Here is our situation which prompted us to take that path: (The path of setting
up a new cluster and migrate from an old cluster rather than performing a
rolling upgrade)
We have two small clusters one running 1.1.4 and one running 1.1.10. We are
having loads of issues with the 1.1.10 cluster (primarily could be because of
the load patterns it experiences and our experiments have shown that the 1.1.10
also degraded in performance over time possibly because of hardware as well).
This has led us to the decision to move to new hardware.
Our new hardware being LCS capable ( we were running with hard disks on the
older clusters ) and at the same time we cant afford a gradual rip off Size
tiered compaction to LCS based SSTables because it will impact our latencies to
a very great extent. Unfortunately we have no backup clusters right now.
Our other tests also made us think about 1.2.4 because of the heap data
structures that 1.2.4 provides us with. GCs have really became a headache for
us and our application requires DB calls to be returned below 15ms time range
(as shown in opscenter). In our tests we saw about 125 % gain in performance as
compared to the hard disk based 1.1.x versions with the same number of nodes.
In this context, we want to merge both the old clusters into a single new
hardware based one and running 1.2.4 with the least amount of downtimes and
application layer impacts.
> Multi-DC not working between 1.1.10 and 1.2.4 version
> -----------------------------------------------------
>
> Key: CASSANDRA-5684
> URL: https://issues.apache.org/jira/browse/CASSANDRA-5684
> Project: Cassandra
> Issue Type: Bug
> Components: Core
> Affects Versions: 1.2.4
> Environment: Linux
> Reporter: Ananth Gundabattula
>
> We wanted to upgrade to a higher version of cassandra ( a custom build of
> 1.2.4 ) from current cassandra version 1.1.10.
> The way we wanted to upgrade is to build a new cluster and enable multi-dc
> replication; rebuild and switch the application layer to the new cluster.
> This enabled us to have the least downtime.
> However, I was not able to get a multi-dc going between these two versions. I
> followed pretty much the instructions here ( for the 1.2.4 version )
> http://www.datastax.com/documentation/cassandra/1.2/index.html#cassandra/operations/ops_add_dc_to_cluster_t.html.
> I tried enabling multi-dc using these instructions for the 1.1.10 cluster
> http://www.datastax.com/docs/1.0/initialize/cluster_init_multi_dc
> Mixing both the approaches did not work either. Specifying a 1.2.4 node as
> one of the 1.1.10 cluster seed nodes caused errors in the startup of 1.2.4
> node. The error was not an exception but a message looking like this in the
> logs : ClusterName mismatch from /10.xxx.xx.xx DC1!=DC2
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