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https://issues.apache.org/jira/browse/BOOKKEEPER-301?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13399165#comment-13399165
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Flavio Junqueira commented on BOOKKEEPER-301:
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Agreed, but that statement is a bit misleading. The force implementation calls
fsync, and if you check the documentation of fsync, it says that it forces the
flush of OS buffers to the disk device. It doesn't guarantee that the disk
device won't cache the data itself. One needs to turn off the disk cache to
avoid that, or use kernel-level barriers. I've seen discussions around about
the implementation of barriers in the linux kernel not being very safe.
We have verified in lab experiments that you can lose data upon crashes, but
way less compared to not forcing at all. I have never seen such a case in a
production setting.
> Chance of Data loss on sudden poweroff
> --------------------------------------
>
> Key: BOOKKEEPER-301
> URL: https://issues.apache.org/jira/browse/BOOKKEEPER-301
> Project: Bookkeeper
> Issue Type: Bug
> Components: bookkeeper-server
> Affects Versions: 4.2.0
> Reporter: Uma Maheswara Rao G
> Assignee: Uma Maheswara Rao G
>
> Whatever data Bookie flushed into disk may not be gauranteed that they are
> really pesisted into device. OS will cache the edits. On suddent power off,
> we may loose that edits.
> This is the JIRA to discuss this problem and address the case.
> Hadoop related issue HDFS-1539.
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