Google does dynamic splitting and merging of regions to deal with hot spots. They had to be careful that they did not oscilate between splitting and merging when the load pattern changed.
Right now, manual merges are ok because we only do splits when regions grow and the only reason to merge is if many rows are deleted. When we get to doing more sophisticated load balancing, we will want the capability of both splitting and merging based on load. > -----Original Message----- > From: Bryan Duxbury (JIRA) [mailto:[EMAIL PROTECTED] > Sent: Monday, January 07, 2008 1:10 PM > To: hadoop-dev@lucene.apache.org > Subject: [jira] Commented: (HADOOP-2405) [hbase] Merge region > tool exposed in shell and/or in UI > > > [ > https://issues.apache.org/jira/browse/HADOOP-2405?page=com.atl assian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=> 12556694#action_12556694 ] > > Bryan Duxbury commented on HADOOP-2405: > --------------------------------------- > > So, you envision the merge operation to not only require > manual triggering but to require manual targeting? Shouldn't > the point of merging regions be to maintain the equilibrium > of size of regions? Under what circumstances will you have to > manually intervene to keep regions appropriately sized? > > It seems like this should really only happen after a > substantial number of deletions has occurred, right? That > would cause a compacted region to shrink below a healthy > size, and if it could be merged with a neighbor, it would be > nice. This logic should be built in and automatic, otherwise > it would require constant monitoring of region sizes by an > administrator. > > Other than this sort of automatic merging, when would you > want to manually merge two regions? Doesn't that expose a > somewhat dangerous amount of functionality to the end user? > > > [hbase] Merge region tool exposed in shell and/or in UI > > ------------------------------------------------------- > > > > Key: HADOOP-2405 > > URL: > https://issues.apache.org/jira/browse/HADOOP-2405 > > Project: Hadoop > > Issue Type: New Feature > > Components: contrib/hbase > > Reporter: stack > > Priority: Minor > > > > hbase has support for merging regions. Expose a merge > trigger in the shell or in the UI (Can only merge adjacent > features so perhaps only makes sense in UI in the regionserver UI). > > -- > This message is automatically generated by JIRA. > - > You can reply to this email to add a comment to the issue online. > > > No virus found in this incoming message. > Checked by AVG Free Edition. > Version: 7.5.516 / Virus Database: 269.17.13/1213 - Release > Date: 1/7/2008 9:14 AM > > No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.516 / Virus Database: 269.17.13/1213 - Release Date: 1/7/2008 9:14 AM
