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https://issues.apache.org/jira/browse/HBASE-8817?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13702960#comment-13702960
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Thomas Pan commented on HBASE-8817:
-----------------------------------
Let me start with the simpler one, regarding flushes. Please verify that my
understanding is correct.
2.3.1.1. HBase Default Configuration
hbase.regionserver.global.memstore.upperLimit
Maximum size of all memstores in a region server before new updates are blocked
and flushes are forced. Defaults to 40% of heap. Updates are blocked and region
level flushes are forced until size of all memstores in a region server hits
hbase.regionserver.global.memstore.lowerLimit.
hbase.hregion.memstore.flush.size
Memstore will be flushed to disk if size of the memstore exceeds this number of
bytes. When that happens, memstores that belong to the same region will all be
flushed. Value is checked by a thread that runs every
hbase.server.thread.wakefrequency.
9.7.6.1. MemStore
The MemStore holds in-memory modifications to the Store. Modifications are
KeyValues. When asked to flush, current memstore is moved to snapshot and is
cleared. HBase continues to serve edits out of new memstore and backing
snapshot until flusher reports in that the flush succeeded. At this point the
snapshot is let go. Note that when flush happens, memstores that belong to the
same region will all be flushed out.
> Enhance The Apache HBase Reference Guide
> ----------------------------------------
>
> Key: HBASE-8817
> URL: https://issues.apache.org/jira/browse/HBASE-8817
> Project: HBase
> Issue Type: Bug
> Components: documentation
> Reporter: Thomas Pan
>
> I am reading the guide here: http://hbase.apache.org/book.html#regions.arch
> I have noticed the following:
> - There is lack of coverage on scan. Note that Lars has a very good
> presentation from last year's HBaseCon:
> http://www.slideshare.net/cloudera/3-learning-h-base-internals-lars-hofhansl-salesforce-final
> - Under section 9.7.6.1, there is no mentioning of flush per region if a
> memstore reached the size threshold (and a possible flush of all memstores if
> over all memory usage of all the memstores reached memstore.upperlimit). Note
> that people need to combine the information provided in section 9 with
> section 2.3.1.1 to fully understand the situation.
> - Compaction tuning strategies. Both Nicolas from Facebook and Sergey from
> Hortonworks have presented various compaction algorithms. Sometime, once all
> the necessary code is in master, we need to have the coverage.
> Let me know how I can help on the matter.
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