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https://issues.apache.org/jira/browse/CASSANDRA-1608?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13091974#comment-13091974
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Jonathan Ellis commented on CASSANDRA-1608:
-------------------------------------------
Committed with some changes:
- Switched DataTracker registration to be eager instead of lazy -- otherwise
sstables created before any compaction happened (during log replay for
instance) would not be added to the manifest. Also added unregistration when a
new Strategy is created on schema change.
- added some debug logging to Manifest
- moved the LevelDB classes from db.leveldb to db.compaction, so that I could
add a "unqualified compaction strategy will be looked for in oac.db.compaction"
rule
- renamed LevelDB* to Leveled*
- ran dos2unix on the intervaltree classes and reformatted
- added code to make it not attempt to compact empty L0, which caused an
assertion error
- Added getUnleveledSSTables to CFSMBean
Still to do:
- CASSANDRA-3085
> 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, 1608-v5.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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