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From "Blake Eggleston (JIRA)" <>
Subject [jira] [Commented] (CASSANDRA-13508) Make system.paxos table compaction strategy configurable
Date Fri, 19 May 2017 22:41:04 GMT


Blake Eggleston commented on CASSANDRA-13508:

I agree, LCS is probably the better choice, which is the default in trunk. I think being able
to tune the paxos table might not be a bad idea, given how heavily it can be used in some
systems, but it also has some risks. First, supporting it won't be straightforward. System
table schemas are hardcoded (see {{SystemKeyspace}}), so just allowing alter table statements
against them isn't enough. Any changes you make will be lost after a node restart. Storing
system table schemas as regular tables is also a non-starter. Any user configurable system
properties are something that would have to be configured in cassandra.yaml or something,
which for non-replicated tables, isn't terrible (and not the same thing as the schema.xml
file used ca 0.6 this will remind people of). [~iamaleksey], do you have any thoughts on this?

> Make system.paxos table compaction strategy configurable
> --------------------------------------------------------
>                 Key: CASSANDRA-13508
>                 URL:
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Jay Zhuang
>            Assignee: Jay Zhuang
>             Fix For: 4.0, 4.x
>         Attachments: test11.png, test2.png
> The default compaction strategy for {{system.paxos}} table is LCS for performance reason:
CASSANDRA-7753. But for CAS heavily used cluster, the system is busy with {{system.paxos}}
> As the data in {{paxos}} table are TTL'ed, TWCS might be a better fit. In our test, it
significantly reduced the number of compaction without impacting the latency too much:
> !test11.png!
> The time window for TWCS is set to 2 minutes for the test.
> Here is the p99 latency impact:
> !test2.png!
> the yellow one is LCS, the purple one is TWCS. Average p99 has about 10% increase.

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