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From Andrew Purtell <apurt...@apache.org>
Subject Re: Zookeeper/Hbase storage type on EC2
Date Sat, 23 Jul 2011 05:42:01 GMT
HBase does not keep any persistent state in ZooKeeper.

You can restart your ZK cluster one peer at a time without affecting HBase.

If you are going to bring your entire ZK cluster down, first shut down HBase. Then once ZK
is started again, bring up HBase.
 
   - Andy

Problems worthy of attack prove their worth by hitting back. - Piet Hein (via Tom White)



----- Original Message -----
> From: Patrick Hunt <phunt@apache.org>
> To: user@zookeeper.apache.org
> Cc: 
> Sent: Thursday, July 21, 2011 3:56 PM
> Subject: Re: Zookeeper/Hbase storage type on EC2
> 
> On Thu, Jul 21, 2011 at 1:21 AM, Yves Langisch <yves@langisch.ch> wrote:
>>  I just need a statement if it makes sense to use ephemeral storage for ZK 
> at
>>  all (in conjunction with Hbase if the answer depends on the use case)?
>> 
>>  Any help is appreciated.
>> 
>> 
>>  On 19.07.2011 19:37, Yves Langisch wrote:
> 
>>>  I plan to setup a HBase installation on EC2. As recommended I therefore
>>>  want to setup a zookeeper ensemble with 3 nodes but I'm not sure 
> what kind
>>>  of storage I've to choose for the two zk directories (dataDir and
>>>  dataLogDir). Do this two directories need to be on a persistent storage
>>>  which survives a node crash? Or does an ephemeral storage device 
> suffice
>>>  since a failed node which is restarted is being synchronized with the 
> other
>>>  two nodes anyway? And what happens when I restart the whole zk ensemble 
> with
>>>  ephemeral storage which means there is no zk data available anymore 
> after
>>>  booting up? Any impact on the Hbase cluster?
> 
> I don't think you want to use ephemeral storage given that HBase would
> lose information if the zk cluster was restarted. But really that's a
> better question for the hbase team, I don't know exactly how they are
> using ZK and the effects of such a loss on their application.
> 
> Regards,
> 
> Patrick
>

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