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From Patrick Hunt <ph...@apache.org>
Subject Re: Zookeeper/Hbase storage type on EC2
Date Mon, 25 Jul 2011 16:33:52 GMT
I was under the impression that there was some persistent data kept in
ZK by hbase, good to know. Perhaps a FAQ entry for this?


On Fri, Jul 22, 2011 at 10:42 PM, Andrew Purtell <apurtell@apache.org> wrote:
> 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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