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https://issues.apache.org/jira/browse/HADOOP-1903?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12527687
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stack commented on HADOOP-1903:
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On second take, if the interruption causes a regionserver crash, there should
be no data loss; memaches is backed upin the hlog. But if we manage to keep
going, then we'll be in a strange situation where the snapshot has been 'lost'
-- though backed up in hlog -- because regionserver serves out of
memcache+snapshot histories and from flushes, the store HStoreFiles.
> [hbase] Data loss if Exception happens between snapshot and flush to disk.
> --------------------------------------------------------------------------
>
> Key: HADOOP-1903
> URL: https://issues.apache.org/jira/browse/HADOOP-1903
> Project: Hadoop
> Issue Type: Bug
> Reporter: stack
>
> There exists a little window during which we can lose data. During a
> memcache flush, we make an inmemory copy, a 'snapshot'. The memcache is then
> zeroed and off we go again taking updates. Meantime, in background we are
> supposed to flush the snapshot to disk. If this process is interrupted --
> e.g. the HDFS is yanked from under us or if an OOME occurs in this thread --
> then the content of the snapshot is lost.
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