incubator-cassandra-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Robert Coli <rc...@digg.com>
Subject Re: Uneven distribution using RP
Date Tue, 22 Jun 2010 17:26:39 GMT
On 6/22/10 10:07 AM, James Golick wrote:
> This node's load is now growing at a ridiculous rate. It is at 105GB, 
> with the next most loaded node at 70.63GB.
>
> Given that RF=3, I would assume that the replicas' nodes would grow 
> relatively quickly too?
What Replica Placement Strategy are you using (Rackunaware, Rackaware, 
etc?)? The current implementation of Rackaware is pretty simple and 
relies on careful placement of nodes in multiple DCs along the ring to 
avoid hotspots.

http://wiki.apache.org/cassandra/Operations#Replication
"
RackAwareStrategy: replica 2 is placed in the first node along the ring 
the belongs in another data center than the first; the remaining N-2 
replicas, if any, are placed on the first nodes along the ring in the 
same rack as the first

Note that with RackAwareStrategy, succeeding nodes along the ring should 
alternate data centers to avoid hot spots. For instance, if you have 
nodes A, B, C, and D in increasing Token order, and instead of 
alternating you place A and B in DC1, and C and D in DC2, then nodes C 
and A will have disproportionately more data on them because they will 
be the replica destination for every Token range in the other data center.
"

https://issues.apache.org/jira/browse/CASSANDRA-785

Is also related, and marked Fix Version 0.8.

=Rob


Mime
View raw message