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Posted to user@cassandra.apache.org by AJ <aj...@dude.podzone.net> on 2011/06/14 23:33:11 UTC

Where is my data?

Is there an official deterministic formula to compute the various 
subsets of a given cluster that comprises a complete set of data 
(redundant rows ok)?  IOW, if multiple nodes become unavailable one at a 
time, at what point can I say <100% of my data is available?

Obviously, the method would have to take into consideration the ring 
layout along with the partition type, the # of nodes, 
replication_factor, replication strat, etc..

Thanks!

Re: Where is my data?

Posted by aaron morton <aa...@thelastpickle.com>.

I wrote a blog post about this sort of thing the other day 
http://thelastpickle.com/2011/06/13/Down-For-Me/

Let me know if you spot any problems. 

Cheers

-----------------
Aaron Morton
Freelance Cassandra Developer
@aaronmorton
http://www.thelastpickle.com

On 16 Jun 2011, at 02:20, AJ wrote:

> Thanks
> 
> On 6/15/2011 3:20 AM, Sylvain Lebresne wrote:
>> You can use the thrift call describe_ring(). It will returns a map
>> that associate to each range of the
>> ring who is a replica. Once any range has all it's endpoint
>> unavailable, that range of the data is unavailable.
>> 
>> --
>> Sylvain
>> 
>

Re: Where is my data?

Posted by AJ <aj...@dude.podzone.net>.

Thanks

On 6/15/2011 3:20 AM, Sylvain Lebresne wrote:
> You can use the thrift call describe_ring(). It will returns a map
> that associate to each range of the
> ring who is a replica. Once any range has all it's endpoint
> unavailable, that range of the data is unavailable.
>
> --
> Sylvain
>

Re: Where is my data?

Posted by Sylvain Lebresne <sy...@datastax.com>.

You can use the thrift call describe_ring(). It will returns a map
that associate to each range of the
ring who is a replica. Once any range has all it's endpoint
unavailable, that range of the data is unavailable.

--
Sylvain

On Tue, Jun 14, 2011 at 11:33 PM, AJ <aj...@dude.podzone.net> wrote:
> Is there an official deterministic formula to compute the various subsets of
> a given cluster that comprises a complete set of data (redundant rows ok)?
>  IOW, if multiple nodes become unavailable one at a time, at what point can
> I say <100% of my data is available?
>
> Obviously, the method would have to take into consideration the ring layout
> along with the partition type, the # of nodes, replication_factor,
> replication strat, etc..
>
> Thanks!
>