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From "stack (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-3779) Allow split regions to be placed on different region servers
Date Tue, 19 Apr 2011 16:48:05 GMT

    [ https://issues.apache.org/jira/browse/HBASE-3779?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13021652#comment-13021652
] 

stack commented on HBASE-3779:
------------------------------

Needs tests to prove it does as advertised

The HMaster change is cleanup of drudge left over from your last balancer improvement?

Does this work?

{code}
-    regionOnline(b, hsi);
+    if (daughterPlacement == DaughterPlacement.SAME_HOST) {
+      regionOnline(b, hsi);
+    } else if (daughterPlacement == DaughterPlacement.ONE_ON_LEAST_LOADED) {
+      if (leastLoadedServer != null) {
+        LOG.info("placing " + b + " on " + leastLoadedServer);
+        regionOnline(b, leastLoadedServer);
+      }
+      else regionOnline(b, hsi);
+    }
{code}

IIRC, this code is tickled when we get report of split.  We are noting in the Master's memory
that the daughters are up on host 'hsi'.  In the above, if ONE_ON_LEAST_LOADED, you are saying
the region is on the least loaded server.  Writing this into Master memory state does not
make it so; the region is still going to be out on the regionserver where the split happened?
 Right?



> Allow split regions to be placed on different region servers
> ------------------------------------------------------------
>
>                 Key: HBASE-3779
>                 URL: https://issues.apache.org/jira/browse/HBASE-3779
>             Project: HBase
>          Issue Type: Improvement
>          Components: master
>    Affects Versions: 0.90.2
>            Reporter: Ted Yu
>            Assignee: Ted Yu
>         Attachments: 3779.patch
>
>
> Currently daughter regions are placed on the same region server where the parent region
was.
> Stanislav Barton mentioned the idea that load information should be considered when placing
the daughter regions.
> The rationale is that the daughter regions tend to receive more writes. So it would be
beneficial to place at least one daughter region on a different region server.

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