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From "Christian Posta (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (AMQ-5578) preallocate journal files
Date Thu, 19 Feb 2015 17:55:12 GMT

    [ https://issues.apache.org/jira/browse/AMQ-5578?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14327803#comment-14327803
] 

Christian Posta commented on AMQ-5578:
--------------------------------------

okay patch updated and committed here: https://github.com/apache/activemq/commit/45e59e6e839ae89ffc099d32a4180ee307543aae

i removed the options to do preallocation in on-demand batches. will do that in a separate
jira. 

with the patch the following functionality is available:

preallocationScope=[entire_journal]
preallocationStrategy=[sparse_file|os_kernel_copy|zeros]

the defaults are "entire_journal", and "sparse_file"

the entire_journal option works great with "zeros", it also works great with "os_kernel_copy"
but depending on your file system. There is a kernel bug related to using GFS2 that we're
fixing at the Red Hat side. 

basically the difference is between the application zero'ing out the journal file for preallocation,
or letting the OS do it in the kernel space.



> preallocate journal files
> -------------------------
>
>                 Key: AMQ-5578
>                 URL: https://issues.apache.org/jira/browse/AMQ-5578
>             Project: ActiveMQ
>          Issue Type: Improvement
>          Components: Message Store
>    Affects Versions: 5.11.0
>            Reporter: Gary Tully
>            Assignee: Gary Tully
>              Labels: journal, kahaDB, perfomance
>
> Our journals are append only, however we use the size to track journal rollover on recovery
and replay. We can improve performance if we never update the size on disk and preallocate
on creation.
> Rework journal logic to ensure size is never updated. This will allow the configuration
option from https://issues.apache.org/jira/browse/AMQ-4947 to be the default.



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