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https://issues.apache.org/jira/browse/HDFS-8955?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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bijaya updated HDFS-8955:
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Description: We do have hedged read which serves redundancy on read
failures due to bad sector/patch in disk. We need to have similar feature for
hdfs write. This feature may come with cost but its something to must have for
use case which needs to guarantee write success regardless of degraded disk
health. Defination of degraded disk is highly debatable but this is what I
would define. "Degraded disk is the disk which fails to read and write
intermittently" (was: This is a placeholder of hdfs related stuff backport
from https://issues.apache.org/jira/browse/HBASE-7509
The quorum read ability should be helpful especially to optimize read outliers
we can utilize "dfs.dfsclient.quorum.read.threshold.millis" &
"dfs.dfsclient.quorum.read.threadpool.size" to enable/disable the hedged read
ability from client side(e.g. HBase), and by using DFSQuorumReadMetrics, we
could export the interested metric valus into client system(e.g. HBase's
regionserver metric).
The core logic is in pread code path, we decide to goto the original
fetchBlockByteRange or the new introduced fetchBlockByteRangeSpeculative per
the above config items.)
> Support 'hedged' write in DFSClient
> -----------------------------------
>
> Key: HDFS-8955
> URL: https://issues.apache.org/jira/browse/HDFS-8955
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: hdfs-client
> Affects Versions: 2.6.0
> Reporter: bijaya
> Assignee: bijaya
>
> We do have hedged read which serves redundancy on read failures due to bad
> sector/patch in disk. We need to have similar feature for hdfs write. This
> feature may come with cost but its something to must have for use case which
> needs to guarantee write success regardless of degraded disk health.
> Defination of degraded disk is highly debatable but this is what I would
> define. "Degraded disk is the disk which fails to read and write
> intermittently"
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