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.
Problems worthy of attack prove their worth by hitting back. - Piet Hein (via Tom White)
----- Original Message -----
> From: Patrick Hunt <[EMAIL PROTECTED]>
> To: [EMAIL PROTECTED]
> 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 <[EMAIL PROTECTED]> wrote:
>> I just need a statement if it makes sense to use ephemeral storage for ZK
>> 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
>>> since a failed node which is restarted is being synchronized with the
>>> two nodes anyway? And what happens when I restart the whole zk ensemble
>>> ephemeral storage which means there is no zk data available anymore
>>> 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.