I’m curious as to how Cassandra evaluates DC boundaries.  Is there anything config-oriented other than setting rack-aware?




From: Sunil Khedar [mailto:sunil@truesparrow.com]
Sent: December 9, 2009 9:11 AM
To: cassandra-user@incubator.apache.org
Subject: Re: Configuring Cassandra


And while adding 2nd DC we have to make sure that, nodes along the ring should alternate data centers to avoid hot spots. As you explained in http://wiki.apache.org/cassandra/Operations

And that can be a tricky. Correct?


On Wed, Dec 9, 2009 at 7:06 PM, Jonathan Ellis <jbellis@gmail.com> wrote:

It should work, but because of the way RAS works you need to have
equal nodes in DCs for it to be balanced.  so, when you do decide to
add the 2nd DC, you should add as many nodes as you have in the first.

On Wed, Dec 9, 2009 at 4:27 AM, Sunil Khedar <sunil@truesparrow.com> wrote:
> "Replication strategy may not be changed without wiping your data and
> starting over."
> To start with I want to have all my nodes in a single DC. But over a time of
> period, nodes will be placed in multiple DCs. In that is it safe to start
> using "RackAwareStrategy" even if nodes are in a single DC? So, that when I
> start using multiple DCs, data wiping won't be required.
> -Sunil
> On Wed, Dec 9, 2009 at 4:27 AM, Jonathan Ellis <jbellis@gmail.com> wrote:
>> On Tue, Dec 8, 2009 at 7:21 AM, Rakesh Sharma <rakrma@gmail.com> wrote:
>> > f) Can I take backups from each node and merge them on a single node? Or
>> > it's not at all required?
>> All you would need to do would be to copy the snapshotted sstables
>> into the data directory on the target node, but I'm not sure why you
>> would want to do that.
>> I wrote http://wiki.apache.org/cassandra/Operations to answer the
>> other questions in more detail. :)
>> -Jonathan