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From Chris Burroughs <chris.burrou...@gmail.com>
Subject vnode + multi dc migration
Date Fri, 11 Oct 2013 22:06:23 GMT
I know there is a good deal of interest [1] on feasible methods for 
enabling vnodes on clusters that did not start with them.

We recently completed a migration from a production cluster not using 
vnodes and in a single DC to one using vnodes in two DCs.  We used the 
"just spin up a new DC and rebuild" strategy instead of shuffle and it 
worked.  The checklist was long but it really wasn't more complicated 
than that.  Thanks to several people in #cassandra for suggesting the 
technique and reviewing procedures.

One oddity we noticed is that when nodes in a new DC join 
(auto_bootstrap:false) CL.ONE performance tanked [2].  The spike is when 
the nodes came online, and the drop is when reads were switched to 
CL.LOCAL_QUORUM  This only happened when the new DC was cross-continent 
(not a logical DC in the same colo).

[1] 
http://mail-archives.apache.org/mod_mbox/cassandra-user/201308.mbox/%3CCAEDUwd12vhRJbPZpVJ6QzTOx3pwU=11HhGKKipGHHGvoSBJwOA@mail.gmail.com%3E

[2] http://i.imgur.com/ZW5Ob8V.png

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