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From Anand Somani <meatfor...@gmail.com>
Subject Re: Urgent:!! Re: Need to maintenance on a cassandra node, are there problems with this process
Date Fri, 19 Aug 2011 18:30:41 GMT
Let me be specific on  lost data -> lost a replica , the other 2 nodes have
replicas

I am running read/write at quorum. At this point I have turned off my
clients from talking to this node. So if that is the case I can potentially
just nodetool repair (without changing IP). But would it be better if I
copied over the data/mykeyspace from another replica and then run repair?

On Fri, Aug 19, 2011 at 11:20 AM, Peter Schuller <
peter.schuller@infidyne.com> wrote:

> > ok, so we just lost the data on that node. are building the raid on it,
> but
> > once it is up what is the best way to bring it back in the cluster
>
> You're saying the raid failed and data is gone?
>
> > just let it come up and run nodetool repair
> > copy data from another node and then run nodetool repair,
> >
> >  do I still need to run repair immeidately if I copy the data? Want to
> > schedule repair for later during non peak hours?
>
> If data is gone, the safe way is to have it re-join the cluster:
>
>   http://wiki.apache.org/cassandra/Operations#Handling_failure
>
> But note that in your case, since you've lost data (if I understand
> you), it's effectively a completely new node. That means you either
> want to switch it's IP address and go for the "recommended" approach,
> or do the other option but that WILL mean the node is serving reads
> with incorrect data, violating the consistency. Depending on your
> application, this may or may not be the case.
>
> Unless it's a major problem for you, I suggest bringing it back in
> with a new IP address and make it be treated like a completely fresh
> replacement node. Probably decreases the risk of mistakes happening.
>
> As for the other stuff about repair in the e-mail you pasted; periodic
> repairs are part of regular cluster maintenance. See:
>
>   http://wiki.apache.org/cassandra/Operations#Frequency_of_nodetool_repair
>
> --
> / Peter Schuller (@scode on twitter)
>

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