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From "Ariel Weisberg (JIRA)" <>
Subject [jira] [Updated] (CASSANDRA-8771) Remove commit log segment recycling
Date Mon, 23 Nov 2015 21:43:11 GMT


Ariel Weisberg updated CASSANDRA-8771:
    Component/s: Local Write-Read Paths

> Remove commit log segment recycling
> -----------------------------------
>                 Key: CASSANDRA-8771
>                 URL:
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Local Write-Read Paths
>            Reporter: Ariel Weisberg
>            Assignee: Ariel Weisberg
>              Labels: commitlog
>             Fix For: 2.2.0 beta 1
> For discussion
> Commit log segment recycling introduces a lot of complexity in the existing code.
> CASSANDRA-8729 is a side effect of commit log segment recycling and addressing it will
require memory management code and thread coordination for memory that the filesystem will
no longer handle for us.
> There is some discussion about what storage configurations actually benefit from preallocated
files. Fast random access devices like SSDs, or non-volatile write caches etc. make the distinction
not that great. 
> I haven't measured any difference in throughput for bulk appending vs overwriting although
it was pointed out that I didn't test with concurrent IO streams.
> What would it take to make removing commit log segment recycling acceptable? Maybe a
benchmark on a spinning disk that measures the performance impact of preallocation when there
are other IO streams?

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