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Date: Mon, 06 Jul 2009 13:52:37 -0700
From: Patrick Hunt <phunt@apache.org>
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To: zookeeper-user@hadoop.apache.org
Subject: Re: zookeeper on ec2
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Ted thanks for the info.

I've created a wiki page
http://wiki.apache.org/hadoop/ZooKeeper/ZooKeeperOnEC2
to capture details of running ZK on EC2. If you or anyone else would 
like to update it with information please do so.

Regards,

Patrick

Ted Dunning wrote:
> I disagree with the original post that this is a problem, even in EC2.
> Having the persistent copy on disk is exactly what makes the rolling restart
> work so well.
> 
> I think that the misunderstanding is that this on-disk image is critical to
> cluster function.  It is not critical because it is replicated to all
> cluster members.  This means that any member can disappear and a new
> instance can replace it with no big cost other than the temporary load of
> copying the current snapshot from some cluster member.
> 
> On Mon, Jul 6, 2009 at 11:33 AM, Mahadev Konar <mahadev@yahoo-inc.com>wrote:
> 
>>  In the documentation of zookeeper, I have read that
>>> zookeeper saves snapshots of the in-memory data in the file system. Is
>>> that needed for recovery? Logically, it would be much easier for me if
>>> this is not the case.
>> Yes, zookeeper keeps persistent state on disk. This is used for recovery
>> and
>> correctness of zookeeper.
>