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From aaron morton <aa...@thelastpickle.com>
Subject Re: [Cassandra] Expanding a Cassandra cluster
Date Thu, 20 Jun 2013 09:23:54 GMT
> 1) Is there any implication in running nodetool repair immediately after bringing a new
node up (before key migration process is completed) ?
>         Will it cause some race conditions ? Or will it result in some part of the space
never be reclaimed ?
Repair will only be concerned with data that the node is replica for. And cleanup is only
concerned with data that the node is no longer a replica for. 
AFAIK they should be able to run concurrently, but I would avoid it incase there are some
edge cases. 

> 2) How can I figure out the status of key migration in Cassandra?
Not sure what you mean by key migration. 
If you are talking about a token move or node bootstrap you can get some idea from nodetool
compactionstats and nodetool netstats. 

FWIW I think nodetool cleanup is less aggressive than repair. Repair reads all the data and
creates a hash, cleanup just reads it from one file and writes a new file dropping rows that
no longer belong. It's probably uses less CPU than compaction as it does not merge row fragments.


Cheers

-----------------
Aaron Morton
Freelance Cassandra Consultant
New Zealand

@aaronmorton
http://www.thelastpickle.com

On 19/06/2013, at 10:48 AM, Emalayan Vairavanathan <svemalayan@yahoo.com> wrote:

> Thank you all.
> 
> I have two more question.
> 
> 1) Is there any implication in running nodetool repair immediately after bringing a new
node up (before key migration process is completed) ?
>         Will it cause some race conditions ? Or will it result in some part of the space
never be reclaimed ?
> 
> 2) How can I figure out the status of key migration in Cassandra?
> 
> Thank you
> Emalayan 
> 
> From: Richard Low <richard@wentnet.com>
> To: user@cassandra.apache.org; Emalayan Vairavanathan <svemalayan@yahoo.com> 
> Sent: Tuesday, 18 June 2013 12:11 AM
> Subject: Re: [Cassandra] Expanding a Cassandra cluster
> 
> On 10 June 2013 22:00, Emalayan Vairavanathan <svemalayan@yahoo.com> wrote:
> 
>                    b) Will Cassandra automatically take care of removing obsolete keys
in future ?
> 
> In a future version Cassandra should automatically clean up for you:
> 
> https://issues.apache.org/jira/browse/CASSANDRA-5051
> 
> Right now though you have to run cleanup eventually or the space will never be reclaimed.
> 
> Richard.
> 
> 


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