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https://issues.apache.org/jira/browse/CASSANDRA-3224?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13108637#comment-13108637
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Brandon Williams commented on CASSANDRA-3224:
---------------------------------------------
+1
> LeveledCompactionStrategy is too complacent
> -------------------------------------------
>
> Key: CASSANDRA-3224
> URL: https://issues.apache.org/jira/browse/CASSANDRA-3224
> Project: Cassandra
> Issue Type: Bug
> Components: Core
> Affects Versions: 1.0.0
> Reporter: Brandon Williams
> Assignee: Jonathan Ellis
> Labels: compaction
> Fix For: 1.0.0
>
> Attachments: 3224-v2.txt, 3224-v3.txt, 3224-v4.txt, 3224-v5.txt,
> 3224-v6.txt, 3224.txt, system.log.bz2
>
>
> As the title says, it barely does anything. I inserted 50G worth of data
> with 1G heap and 99% overwrite ratio, and it only compacted twice:
> {noformat}
> INFO [CompactionExecutor:1] 2011-09-16 22:29:54,572 CompactionTask.java
> (line 118) Compacting
> [SSTableReader(path='/var/lib/cassandra/data/Keyspace1/Standard1-h-1-Data.db')]
> INFO [CompactionExecutor:1] 2011-09-16 22:29:58,606 CompactionTask.java
> (line 220) Compacted to
> [/var/lib/cassandra/data/Keyspace1/Standard1-h-2-Data.db,/var/lib/cassandra/data/Keyspace1/Standard1-h-4-Data.db,/var/lib/cassandra/data/Keyspace1/Standard1-h-5-Data.db,].
> 12,595,811 to 12,595,811 (~100% of original) bytes for 40,501 keys at
> 3.058122MBPS. Time: 3,928ms.
> INFO [CompactionExecutor:1] 2011-09-16 22:29:58,607 CompactionTask.java
> (line 222) CF Total Bytes Compacted: 12,595,811
> INFO [CompactionExecutor:3] 2011-09-16 22:29:58,889 CompactionTask.java
> (line 118) Compacting
> [SSTableReader(path='/var/lib/cassandra/data/Keyspace1/Standard1-h-4-Data.db'),
>
> SSTableReader(path='/var/lib/cassandra/data/Keyspace1/Standard1-h-2-Data.db'),
>
> SSTableReader(path='/var/lib/cassandra/data/Keyspace1/Standard1-h-5-Data.db'),
>
> SSTableReader(path='/var/lib/cassandra/data/Keyspace1/Standard1-h-3-Data.db')]
> INFO [CompactionExecutor:3] 2011-09-16 22:30:06,900 CompactionTask.java
> (line 220) Compacted to
> [/var/lib/cassandra/data/Keyspace1/Standard1-h-7-Data.db,/var/lib/cassandra/data/Keyspace1/Standard1-h-9-Data.db,/var/lib/cassandra/data/Keyspace1/Standard1-h-11-Data.db,/var/lib/cassandra/data/Keyspace1/Standard1-h-12-Data.db,/var/lib/cassandra/data/Keyspace1/Standard1-h-14-Data.db,/var/lib/cassandra/data/Keyspace1/Standard1-h-15-Data.db,].
> 28,374,396 to 28,374,396 (~100% of original) bytes for 91,236 keys at
> 3.380379MBPS. Time: 8,005ms.
> INFO [CompactionExecutor:3] 2011-09-16 22:30:06,901 CompactionTask.java
> (line 222) CF Total Bytes Compacted: 40,970,207
> {noformat}
> Resulting in the following levels:
> {noformat}
> L0: 4965
> L1: 6
> L2: 0
> L3: 0
> L4: 0
> L5: 0
> L6: 0
> L7: 0
> {noformat}
> This is obviously going to result in extremely poor read performance.
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