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HBASE-13883 Clarify the MemStore Flush section in the RefGuide

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Misty Stanley-Jones 2015-12-18 11:04:52 -08:00
parent 61a5ef9e65
commit fea0dd46dd
1 changed files with 20 additions and 7 deletions
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src/main/asciidoc/_chapters/architecture.adoc
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@ -1509,13 +1509,26 @@ Note that when the flush happens, MemStores that belong to the same region will
A MemStore flush can be triggered under any of the conditions listed below.
The minimum flush unit is per region, not at individual MemStore level.
. When a MemStore reaches the size specified by `hbase.hregion.memstore.flush.size`, all MemStores that belong to its region will be flushed out to disk.
. When the overall MemStore usage reaches the value specified by `hbase.regionserver.global.memstore.upperLimit`, MemStores from various regions will be flushed out to disk to reduce overall MemStore usage in a RegionServer.
. When a MemStore reaches the size specified by `hbase.hregion.memstore.flush.size`,
all MemStores that belong to its region will be flushed out to disk.
. When the overall MemStore usage reaches the value specified by
`hbase.regionserver.global.memstore.upperLimit`, MemStores from various regions
will be flushed out to disk to reduce overall MemStore usage in a RegionServer.
+
The flush order is based on the descending order of a region's MemStore usage.
Regions will have their MemStores flushed until the overall MemStore usage drops to or slightly below `hbase.regionserver.global.memstore.lowerLimit`.
. When the number of WAL per region server reaches the value specified in `hbase.regionserver.max.logs`, MemStores from various regions will be flushed out to disk to reduce WAL count.
+
Regions will have their MemStores flushed until the overall MemStore usage drops
to or slightly below `hbase.regionserver.global.memstore.lowerLimit`.
. When the number of WAL log entries in a given region server's WAL reaches the
value specified in `hbase.regionserver.max.logs`, MemStores from various regions
will be flushed out to disk to reduce the number of logs in the WAL.
+
The flush order is based on time.
Regions with the oldest MemStores are flushed first until WAL count drops below `hbase.regionserver.max.logs`.
+
Regions with the oldest MemStores are flushed first until WAL count drops below
`hbase.regionserver.max.logs`.
[[hregion.scans]]
==== Scans