Riak replication and quorum

Peter Fales Peter.Fales at alcatel-lucent.com
Fri May 13 11:13:58 EDT 2011


I'm a Riak newbie, trying to get some familiarity with the system by
runing some tests on Amazon EC2.   I'm seeing some behavior that I don't 
understand...

I've set up a test where I create a 4-node cluster using 4 EC2 machines.
I've created a bucket with n_val=4, r=quorum, and w=quorum.   For
n_val=4, the quorum should be 3, so I thought I would have to have at
least 3 nodes in service for my read and write operations to succeed.
During my test, I start sending read/write requests to two of the nodes
(and I see the CPU load go up on all four nodes, so I know they are
talking to each other).  Then I reboot the other two nodes.  At that 
point, I was expecting the reads and writes to start failing, but in 
fact I usually don't see any problems.  (sometimes the query that is 
in progress at the time may fail or timeout, but if I establish a new
connection to the server, and start sending read/write requests again,
those requests will go through, even with only two of the 4 nodes in service)

I suspect I'm just missing something obvious, but I don't understand how
I can run with just two nodes.  What am I missing?

-- 
Peter Fales
Alcatel-Lucent
Member of Technical Staff
1960 Lucent Lane
Room: 9H-505
Naperville, IL 60566-7033
Email: Peter.Fales at alcatel-lucent.com
Phone: 630 979 8031




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