[jira] [Commented] (HBASE-25769) Update default weight of cost functions

["Clara Xiong (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-25769?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17360329#comment-17360329 ] 

Clara Xiong commented on HBASE-25769:
-------------------------------------

We cannot set bytable on because we are dominated by a couple of large tables. If we only move one table at a time, during the move, it will create significant impact on the balance sensitive table scans on other others too.

We have meta table which has a couple of regions/replica fewer than the node count, like many other users.

> Update default weight of cost functions
> ---------------------------------------
>
>                 Key: HBASE-25769
>                 URL: https://issues.apache.org/jira/browse/HBASE-25769
>             Project: HBase
>          Issue Type: Sub-task
>          Components: Balancer
>            Reporter: Clara Xiong
>            Priority: Major
>
> In production, we have seen some critical big tables that handle majority of the load. Table Skew is becoming more important. With the update of table skew function, balancer finally works for large table distribution on large cluster. We should increase the weight from 35 to a level comparable to region count skew: 500. We can even push further to replace region count skew by table skew since the latter works in the same way and account for region distribution per node.
> Another weight we found helpful to increase is for store file size cost function. Ideally if normalizer works perfectly, we don't need to worry about it since region count skew would have accounted for it. But we are often in a situation it doesn't. Store file distribution needs to be given more way as accommodation. we tested changing it from 5 to 200 and it works fine.



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