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https://issues.apache.org/jira/browse/HDFS-3510?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13401658#comment-13401658
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Suresh Srinivas commented on HDFS-3510:
---------------------------------------
Could the logic be simplified- you could just write the
MIN_PREALLOCATION_LENGTH buffer multiple times:
{noformat}
if (need <= 0) {
return;
}
while(need > 0) {
fill.position(0);
IOUtils.writeFully(fc, fill, size);
need -= fillCapacity;
size += fillCapacity;
}
{noformat}
> Improve FSEditLog pre-allocation
> --------------------------------
>
> Key: HDFS-3510
> URL: https://issues.apache.org/jira/browse/HDFS-3510
> Project: Hadoop HDFS
> Issue Type: Bug
> Affects Versions: 1.0.0, 2.0.0-alpha
> Reporter: Colin Patrick McCabe
> Assignee: Colin Patrick McCabe
> Fix For: 1.0.0, 2.0.1-alpha
>
> Attachments: HDFS-3510-b1.001.patch, HDFS-3510-b1.002.patch,
> HDFS-3510.001.patch, HDFS-3510.003.patch, HDFS-3510.004.patch,
> HDFS-3510.004.patch, HDFS-3510.006.patch, HDFS-3510.007.patch,
> HDFS-3510.008.patch, HDFS-3510.009.patch, HDFS-3510.010.patch
>
>
> It is good to avoid running out of space in the middle of writing a batch of
> edits, because when it happens, we often get partial edits at the end of the
> log.
> Edit log preallocation can solve this problem (see HADOOP-2330 for a full
> description of edit log preallocation).
> The current pre-allocation code was introduced for performance reasons, not
> for preventing partial edits. As a consequence, we sometimes do a write
> without using pre-allocation. We should change the pre-allocation code so
> that it always preallocates at least enough space before writing out the
> edits.
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