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https://issues.apache.org/jira/browse/CASSANDRA-1608?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13090275#comment-13090275
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Jonathan Ellis commented on CASSANDRA-1608:
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bq. I assumed that as I was doing operations on these SSTables in the
referenced views I would also need to use these referenced.
Right, but isn't that already the case pre-1608?
I'm just trying to understand if this fixes an existing bug, or if I'm missing
how the usage changed.
bq. Yes this is a potentially serious issue. This code gets called on every
read.
Feels like DataTracker is the wrong granularity to be doing reference counting
at. I'd like to see if we can push that into SSTableReader instead. But let's
do that in another ticket, for our purposes here correctness will suffice and
we can optimize later.
> Redesigned Compaction
> ---------------------
>
> Key: CASSANDRA-1608
> URL: https://issues.apache.org/jira/browse/CASSANDRA-1608
> Project: Cassandra
> Issue Type: Improvement
> Components: Core
> Reporter: Chris Goffinet
> Assignee: Benjamin Coverston
> Attachments: 1608-22082011.txt, 1608-v2.txt, 1608-v4.txt
>
>
> After seeing the I/O issues in CASSANDRA-1470, I've been doing some more
> thinking on this subject that I wanted to lay out.
> I propose we redo the concept of how compaction works in Cassandra. At the
> moment, compaction is kicked off based on a write access pattern, not read
> access pattern. In most cases, you want the opposite. You want to be able to
> track how well each SSTable is performing in the system. If we were to keep
> statistics in-memory of each SSTable, prioritize them based on most accessed,
> and bloom filter hit/miss ratios, we could intelligently group sstables that
> are being read most often and schedule them for compaction. We could also
> schedule lower priority maintenance on SSTable's not often accessed.
> I also propose we limit the size of each SSTable to a fix sized, that gives
> us the ability to better utilize our bloom filters in a predictable manner.
> At the moment after a certain size, the bloom filters become less reliable.
> This would also allow us to group data most accessed. Currently the size of
> an SSTable can grow to a point where large portions of the data might not
> actually be accessed as often.
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