[jira] [Comment Edited] (HBASE-10873) Control number of regions assigned to backup masters

["Jimmy Xiang (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-10873?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13974436#comment-13974436 ] 

Jimmy Xiang edited comment on HBASE-10873 at 4/21/14 4:00 PM:
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bq. Are you concerned with the failover?
Yes, that's the concern here. I was thinking later on, we can open the meta on the backup master as well after we support opening a region in multiple servers. This way, it will be much fast to fail over an active master change.

As to the weight, basically, it means how many regions to host by a backup master compared to a normal region server. The default is 4, i.e. by default, the number of regions opened on a backup master is 1/4 of the number of regions opened on a normal region server. Should we set the default value to 1 (backup master is treated the same as a normal region server) or a big number (less regions)?  If big, how big should be proper?

If we set the weight to 1, it means there is no default behavior change: you can just ignore the new configuration parameter; in the meantime, others can fine-tune it and get more flexibility if needed.



was (Author: jxiang):
bq Are you concerned with the failover?
Yes, that's the concern here. I was thinking later on, we can open the meta on the backup master as well after we support opening a region in multiple servers. This way, it will be much fast to fail over an active master change.

As to the weight, basically, it means how many regions to host by a backup master compared to a normal region server. The default is 4, i.e. by default, the number of regions opened on a backup master is 1/4 of the number of regions opened on a normal region server. Should we set the default value to 1 (backup master is treated the same as a normal region server) or a big number (less regions)?  If big, how big should be proper?

> Control number of regions assigned to backup masters
> ----------------------------------------------------
>
>                 Key: HBASE-10873
>                 URL: https://issues.apache.org/jira/browse/HBASE-10873
>             Project: HBase
>          Issue Type: Improvement
>          Components: Balancer
>            Reporter: Jimmy Xiang
>            Assignee: Jimmy Xiang
>             Fix For: 0.99.0
>
>         Attachments: hbase-10873.patch, hbase-10873_v2.patch
>
>
> By default, a backup master is treated just like another regionserver. So it can host as many regions as other regionserver does. When the backup master becomes the active one, region balancer needs to move those user regions on this master to other region servers. To minimize the impact, it's better not to assign too many regions on backup masters. It may not be good to leave the backup masters idle and not host any region either.
> We should make this adjustable so that users can control how many regions to assign to each backup master.



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