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From Sorin Julean <sorin.jul...@gmail.com>
Subject memtable flush thresholds
Date Mon, 12 Sep 2011 11:55:55 GMT
Hi,

 I've checked the memtable flush (cassandra 0.8.4)  and it seams to me it
hapens sooner then the threshold is reached.

Here's the threshould's (the default ones calculated for a heap size of
-Xmx1980M):
    ColumnFamily: idx_graphable (Super)
      Key Validation Class: org.apache.cassandra.db.marshal.BytesType
      Default column value validator:
org.apache.cassandra.db.marshal.BytesType
      Columns sorted by:
org.apache.cassandra.db.marshal.UTF8Type/org.apache.cassandra.db.marshal.UTF8Type
      Row cache size / save period in seconds: 0.0/0
      Key cache size / save period in seconds: 200000.0/14400
      *Memtable thresholds: 0.5671875/1440/121 (millions of ops/minutes/MB)*
      GC grace seconds: 864000
      Compaction min/max thresholds: 4/32
      Read repair chance: 1.0
      Replicate on write: true

In the logs it seams to me none oh the thresold is reached ( definitively
minutes threshold is not reached ).

9-08 20:12:30,136 MeteredFlusher.java (line 62) flushing high-traffic column
family ColumnFamilyStore(table='graph', columnFamily='idx_graphable')
 INFO [NonPeriodicTasks:1] 2011-09-08 20:12:30,144 ColumnFamilyStore.java
(line 1036) Enqueuing flush of
Memtable-idx_graphable@915643571*(4671498/96780112
serialized/live bytes, 59891 ops)*
 INFO [FlushWriter:111] 2011-09-08 20:12:30,145 Memtable.java (line 237)
Writing Memtable-idx_graphable@915643571(4671498/96780112 serialized/live
bytes, 59891 ops)
 INFO [FlushWriter:111] 2011-09-08 20:12:30,348 Memtable.java (line 254)
Completed flushing [...]/cassandra/data/graph/idx_graphable-g-23-Data.db
(4673905 bytes)


Could someone clarify it for me ?
"high-traffic column family" has a special meaning ?

Many thanks,
Sorin

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