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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (CASSANDRA-7040) Replace read/write stage with per-disk access coordination
Date Wed, 04 Feb 2015 15:27:35 GMT

     [ https://issues.apache.org/jira/browse/CASSANDRA-7040?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Jonathan Ellis updated CASSANDRA-7040:
--------------------------------------
    Fix Version/s:     (was: 3.0)
                   3.1

All right, let's move to 3.1 with 5863.

> Replace read/write stage with per-disk access coordination
> ----------------------------------------------------------
>
>                 Key: CASSANDRA-7040
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-7040
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Benedict
>              Labels: performance
>             Fix For: 3.1
>
>
> As discussed in CASSANDRA-6995, current coordination of access to disk is suboptimal:
instead of ensuring disk accesses alone are coordinated, we instead coordinate at the level
of operations that may touch the disks, ensuring only so many are proceeding at once. As such,
tuning is difficult, and we incur unnecessary delays for operations that would not touch the
disk(s).
> Ideally we would instead simply use a shared coordination primitive to gate access to
the disk when we perform a rebuffer. This work would dovetail very nicely with any work in
CASSANDRA-5863, as we could prevent any blocking or context switching for data that we know
to be cached. It also, as far as I can tell, obviates the need for CASSANDRA-5239.



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