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https://issues.apache.org/jira/browse/HBASE-4246?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13397290#comment-13397290
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Laxman commented on HBASE-4246:
-------------------------------

This may come in latest version also as we didn't change the znode hierarchy of 
the unassigned regions. As mentioned in linked issue, there is a cap on packet 
length. We can't read/write huge data in a single packet.

IMO, to resolve this we need to do *either of the following*.

* In HBASE: We can use hierarchical structure. 
HDFS datanode follows similar strategy. It keeps block files in different sub 
directories to avoid FS lookup latency.

* In ZooKeeper: Increase the limit. What is reasonable?
We have tried this out in some other project but it has the side effects. When 
we tried read/write huge data from ZooKeeper, clients occassionally gets 
disconnected. This is sequential request processing. Please check out the 
related discussions @

http://mail-archives.apache.org/mod_mbox/zookeeper-user/201007.mbox/%3cc85a33ec.3a46a%25maha...@yahoo-inc.com%3E

Following JIRA and discussion also applicable in current scenario.
http://mail-archives.apache.org/mod_mbox/zookeeper-user/201104.mbox/%3cffa3bdb6-1c83-42b9-b2a0-767513462...@me.com%3E
https://issues.apache.org/jira/browse/ZOOKEEPER-1049
                
> Cluster with too many regions cannot withstand some master failover scenarios
> -----------------------------------------------------------------------------
>
>                 Key: HBASE-4246
>                 URL: https://issues.apache.org/jira/browse/HBASE-4246
>             Project: HBase
>          Issue Type: Bug
>          Components: master, zookeeper
>    Affects Versions: 0.90.4
>            Reporter: Todd Lipcon
>            Priority: Critical
>             Fix For: 0.96.0
>
>
> We ran into the following sequence of events:
> - master startup failed after only ROOT had been assigned (for another reason)
> - restarted the master without restarting other servers. Since there was at 
> least one region assigned, it went through the failover code path
> - master scanned META and inserted every region into /hbase/unassigned in ZK.
> - then, it called "listChildren" on the /hbase/unassigned znode, and crashed 
> with "Packet len6080218 is out of range!" since the IPC response was larger 
> than the default maximum.

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