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https://issues.apache.org/jira/browse/HBASE-1730?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13005406#comment-13005406
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stack commented on HBASE-1730:
------------------------------

Ryan suggests that perhaps we not store the schema in ZK, but instead, in a 
schemas catalog table.  We'd use zk though to notify all about schemas changes.

> Near-instantaneous online schema and table state updates
> --------------------------------------------------------
>
>                 Key: HBASE-1730
>                 URL: https://issues.apache.org/jira/browse/HBASE-1730
>             Project: HBase
>          Issue Type: Improvement
>            Reporter: Andrew Purtell
>            Assignee: stack
>             Fix For: 0.92.0
>
>         Attachments: 1730-v2.patch, 1730-v3.patch, 1730.patch
>
>
> We should not need to take a table offline to update HCD or HTD. 
> One option for that is putting HTDs and HCDs up into ZK, with mirror on disk 
> catalog tables to be used only for cold init scenarios, as discussed on IRC. 
> In this scheme, regionservers hosting regions of a table would watch 
> permanent nodes in ZK associated with that table for schema updates and take 
> appropriate actions out of the watcher. In effect, schema updates become 
> another item in the ToDo list.
> {{/hbase/tables/<table-name>/schema}}
> Must be associated with a write locking scheme also handled with ZK 
> primitives to avoid situations where one concurrent update clobbers another. 

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