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Posted to commits@cassandra.apache.org by "Dmitry Konstantinov (Jira)" <ji...@apache.org> on 2026/05/10 10:38:00 UTC
[jira] [Commented] (CASSANDRA-21134) Direct IO support for background writes
[ https://issues.apache.org/jira/browse/CASSANDRA-21134?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18079813#comment-18079813 ]
Dmitry Konstantinov commented on CASSANDRA-21134:
-------------------------------------------------
two other write background operations probably to consider:
* caches periodic saving
* hints writing
> Direct IO support for background writes
> ---------------------------------------
>
> Key: CASSANDRA-21134
> URL: https://issues.apache.org/jira/browse/CASSANDRA-21134
> Project: Apache Cassandra
> Issue Type: Improvement
> Components: Local/SSTable
> Reporter: Sam Lightfoot
> Assignee: Sam Lightfoot
> Priority: Normal
> Fix For: 6.x
>
> Attachments: image-2026-02-11-17-22-58-361.png, image-2026-02-11-17-25-58-329.png, image-2026-03-06-22-05-34-147.png, image-2026-03-07-10-47-44-878.png
>
>
> Follow-up from the implementation for compaction reads (CASSANDRA-19987)
> Notable points
> * Update the start-up check that impacts DIO writes ({_}checkKernelBug1057843{_})
> * RocksDB uses 1 MB flush buffer. This should be configurable and performance tested (256KB vs 1MB)
> * Introduce compaction_write_disk_access_mode / backgroud_write_disk_access_mode
> * Support for the compressed path would be most beneficial
>
> |OperationType|Writes Data|Direct IO|Reason|
> |COMPACTION|Yes|Yes| |
> |TOMBSTONE_COMPACTION|Yes|Yes| |
> |MAJOR_COMPACTION|Yes|Yes| |
> |CLEANUP|Yes|Yes| |
> |UPGRADE_SSTABLES|Yes|Yes| |
> |GARBAGE_COLLECT|Yes|Yes| |
> |ANTICOMPACTION|Yes|Yes| |
> |WRITE|Yes|Yes| |
> |STREAM|Yes|Yes|Supersedes CASSANDRA-20087|
> |SCRUB|Yes|No|Maybe: uses `mark()`/`resetAndTruncate()` for corrupt rollback. Requires additional plumbing.|
> |FLUSH|Yes|No|Excluded: flushed data benefits from page cache due to read recency|
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