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From Peter Schuller <>
Subject Re: RFC: Cassandra Virtual Nodes
Date Mon, 19 Mar 2012 23:45:55 GMT
(I may comment on other things more later)

> As a side note: vnodes fail to provide solutions to node-based limitations
> that seem to me to cause a substantial portion of operational issues such
> as impact of node restarts / upgrades, GC and compaction induced latency. I

Actually, it does. At least assumign DF > RF (as in the original
proposal, and mine). The impact of a node suffering from a performance
degradation is mitigated because the effects are spread out over DF-1
(N-1 in the original post) nodes instead of just RF nodes.

> think some progress could be made here by allowing a "pack" of independent
> Cassandra nodes to be ran on a single host; somewhat (but nowhere near
> entirely) similar to a pre-fork model used by some UNIX-based servers.

I have pretty significant knee-jerk negative reactions to that idea to
be honest, even if the pack is limited to a handful of instances. In
order for vnodes to be useful with random placement, we'd need much
more than a handful of vnodes per node (cassandra instances in a
"pack" in that model).

/ Peter Schuller (@scode,

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