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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.
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.
The flush order is based on time.
Regions with the oldest MemStores are flushed first until WAL count drops below `hbase.regionserver.max.logs`.
. 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 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`.
[[hregion.scans]]
==== Scans