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From Eric Evans <eev...@acunu.com>
Subject Re: RFC: Cassandra Virtual Nodes
Date Tue, 20 Mar 2012 03:24:00 GMT
On Mon, Mar 19, 2012 at 9:37 PM, Vijay <vijay2win@gmail.com> wrote:
> I also did create a ticket
> https://issues.apache.org/jira/browse/CASSANDRA-3768 with some of the
> reason why I would like to see vnodes in cassandra.
> It can also potentially reduce the SSTable seeks which a node has to do to
> query data in SizeTireCompaction if extended to the filesystem.
>
> But 110% agree with Peter, we need to take incremental steps and start with
> the existing bootstrapping.

I'm guessing you're referring to Rick's proposal about ranges per node?

> May be we can start it by making a set of Ranges/Token to a node insted of
> one token. And then may be building things around the movement of those
> ranges.

> I have been thinking about this for a while but having trouble to get to a
> point where i am comfortable changing big chunks of code.

It might help to see some more detail in the proposals.  Both ideas
seem invasive, vnodes more so, but there are many more benefits as
well.

> On Mon, Mar 19, 2012 at 4:45 PM, Peter Schuller <peter.schuller@infidyne.com
>> wrote:
>
>> (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).


-- 
Eric Evans
Acunu | http://www.acunu.com | @acunu

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