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From "Christian Posta (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (AMQ-5578) preallocate journal files
Date Wed, 18 Feb 2015 23:54:12 GMT

    [ https://issues.apache.org/jira/browse/AMQ-5578?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14326758#comment-14326758
] 

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

with the patch, we can now add:

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

the defaults are "entire_journal", "sparse_file", and 1048576

the entire_journal option works great with "zeros", 
it may crash because of a kernel bug related to GFS2 at the moment (to be patched) with "os_kernel_copy"
but may work better for other file systems

still trying to get the batch allocation to work properly, which will allocate space in the
journal with zeros in 1 MB batches as the journal grows, without having to do a big-bang preallocation
of the journal when it gets rotated.



> 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
>             Fix For: 5.12.0
>
>
> 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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