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https://issues.apache.org/jira/browse/CASSANDRA-4142?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13252526#comment-13252526
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Sylvain Lebresne commented on CASSANDRA-4142:
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bq. The comments in CRAR say that it can't use super.read, so is the RAR buffer
wasted?
The buffer in CRAR is for compressed data, the one in RAR is for uncompressed
data, so we do need both.
bq. Not sure how badly validation needs all of these at once.
It doesn't. I haven't given it much though yet, but I think the easiest
way/more efficient way to deal with that would be to have only have 1 sstable
per level loaded (and all of L0), which should always be reasonable.
> OOM Exception during repair session with LeveledCompactionStrategy
> ------------------------------------------------------------------
>
> Key: CASSANDRA-4142
> URL: https://issues.apache.org/jira/browse/CASSANDRA-4142
> Project: Cassandra
> Issue Type: Improvement
> Components: Core
> Affects Versions: 1.0.6
> Environment: OS: Linux CentOs 6
> JDK: Java HotSpot(TM) 64-Bit Server VM (build 14.0-b16, mixed mode)
> Node configuration:
> Quad-core
> 10 GB RAM
> Xmx set to 2,5 GB (as computed by default).
> Reporter: Romain Hardouin
>
> We encountered an OOM Exception on 2 nodes during repair session.
> Our CF are set up to use LeveledCompactionStrategy and SnappyCompressor.
> These two options used together maybe the key to the problem.
> Despite of setting XX:+HeapDumpOnOutOfMemoryError, no dump have been
> generated.
> Nonetheless a memory analysis on a live node doing a repair reveals an
> hotspot: an ArrayList of SSTableBoundedScanner which appears to contain as
> many objects as there are SSTables on disk.
> This ArrayList consumes 786 MB of the heap space for 5757 objects. Therefore
> each object is about 140 KB.
> Eclipse Memory Analyzer's denominator tree shows that 99% of a
> SSTableBoundedScanner object's memory is consumed by a
> CompressedRandomAccessReader which contains two big byte arrays.
> Cluster information:
> 9 nodes
> Each node handles 35 GB (RandomPartitioner)
> This JIRA was created following this discussion:
> http://cassandra-user-incubator-apache-org.3065146.n2.nabble.com/Why-so-many-SSTables-td7453033.html
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