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From "Pavel Yaskevich (Commented) (JIRA)" <>
Subject [jira] [Commented] (CASSANDRA-3948) SequentialWriter doesn't fsync() before posix_fadvise()
Date Thu, 23 Feb 2012 13:15:48 GMT


Pavel Yaskevich commented on CASSANDRA-3948:

We algorithm behind it - we do fadvice(fd, <start_position>, 0) after each 128MB of
data written, flush is done in the process of each re-buffer (which is each 64KB by default)
so we can skip doing sync when we do fadvice() and just use 0 which would hint kernel so skip
everything starting from <start_position>. 
> SequentialWriter doesn't fsync() before posix_fadvise()
> -------------------------------------------------------
>                 Key: CASSANDRA-3948
>                 URL:
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>            Reporter: Peter Schuller
>            Assignee: Pavel Yaskevich
>             Fix For: 1.1.0
> This should make the fadvising useless (mostly). See CASSANDRA-1470 for why, including
links to kernel source. I have not investigated the history of when this broke or whether
it was like from the beginning.
> For the record I have not confirmed this by testing, only by code inspection. I happened
to notice it working on other things, so there is some chance that I'm just mis-reading the

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