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From Rakesh R <rake...@huawei.com>
Subject RE: Ramdisk for dataDir and dataLogDir?
Date Thu, 25 Sep 2014 06:22:39 GMT
I'd like to share one note.

Say, you have a very large datastore(depends on your system). During startup, it can take
considerable amount time for the leader to communicate the znode data to the followers(considering
the n/w transfer rate). initLimit is the amount of time the leader will allow the followers
to get the data from the leader and get to a point where they are ready to serve requests
to clients. If this time is exceeded the leader will close the connection to the follower
and the quorum process will restart. 

Please have a look at the 'initLimit' and 'syncLimit' parameters in zookeeper and tune it.
Probably you can have a test with large datastore(in GBs). I'm interested to know few things
like:
1) zk version
2) are you using ramfs or tmpfs(I think doesn't matter to zk service, but for my understanding)

Also, it would be great if you can share the results in the community. All the best!

Cheers,
Rakesh
-----Original Message-----
From: jlindwall [mailto:jlindwall@yahoo.com] 
Sent: 25 September 2014 00:21
To: zookeeper-user@hadoop.apache.org
Subject: Re: Ramdisk for dataDir and dataLogDir?

I simulated this situation by bringing down one node, deleting its version-2 directory tree,
and restarting the node.  It rejoined and synched up to the existing ensemble just fine.

>From that evidence and the verbiage in the admin guide, I'll trust in this approach to
work.  Of course, I realize when we bring up a failed node in this manner it needs to do a
full sync with the leader which will involve a single SNAP transfer and some transaction log
replays.  We are willing to accept that price.



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