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 <maha...@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.

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