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https://issues.apache.org/jira/browse/HDFS-13709?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16895552#comment-16895552
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Wei-Chiu Chuang commented on HDFS-13709:
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Additionally, while I think the patch is good, the block scanner (VolumeScanner
class) uses BlockSender to detect checksum verification error, so what you do
duplicates the logic there.
{code:title=VolumeScanner#scanBlock()}
try {
blockSender = new BlockSender(block, 0, -1,
false, true, true, datanode, null,
CachingStrategy.newDropBehind());
throttler.setBandwidth(bytesPerSec);
long bytesRead = blockSender.sendBlock(nullStream, null, throttler);
resultHandler.handle(block, null);
metrics.incrBlocksVerified();
return bytesRead;
} catch (IOException e) {
resultHandler.handle(block, e);
}
{code}
It would be great if we can consolidate the error handling to support both
cases.
> Report bad block to NN when transfer block encounter EIO exception
> ------------------------------------------------------------------
>
> Key: HDFS-13709
> URL: https://issues.apache.org/jira/browse/HDFS-13709
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: datanode
> Reporter: Chen Zhang
> Assignee: Chen Zhang
> Priority: Major
> Attachments: HDFS-13709.patch
>
>
> In our online cluster, the BlockPoolSliceScanner is turned off, and sometimes
> disk bad track may cause data loss.
> For example, there are 3 replicas on 3 machines A/B/C, if a bad track occurs
> on A's replica data, and someday B and C crushed at the same time, NN will
> try to replicate data from A but failed, this block is corrupt now but no one
> knows, because NN think there is at least 1 healthy replica and it keep
> trying to replicate it.
> When reading a replica which have data on bad track, OS will return an EIO
> error, if DN reports the bad block as soon as it got an EIO, we can find
> this case ASAP and try to avoid data loss
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