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https://issues.apache.org/jira/browse/HDFS-5153?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Arpit Agarwal updated HDFS-5153:
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Description:
When the number of blocks on the DataNode grows large we start running into a
few issues:
# Block reports take a long time to process on the NameNode. In testing we have
seen that a block report with 6 Million blocks takes close to one second to
process on the NameNode. The NameSystem write lock is held during this time.
# We start hitting the default protobuf message limit of 64MB somewhere around
10 Million blocks. While we can increase the message size limit it already
takes over 7 seconds to serialize/unserialize a block report of this size.
HDFS-2832 has introduced the concept of a DataNode as a collection of storages
i.e. the NameNode is aware of all the volumes attached to a given DataNode.
this makes it easy to split block reports from the DN by sending one report per
attached storage.
was:
When the number of blocks on the DataNode grows large we start running into a
few issues:
# Block reports take a long time to process on the NameNode. In testing we have
seen that a block report with 6 Million blocks takes close to one second to
process on the NameNode. The NameSystem write lock is held during this time.
# We start hitting the default protobuf message limit of 64MB somewhere around
10 Million blocks. While we can increase the message size limit it already
takes over 7 seconds to serialize/unserialize a block report of this size.
HDFS-2832 has introduced the concept of a DataNode as a collection of storages
i.e. we can
> Datanode should stagger block reports from individual storages
> --------------------------------------------------------------
>
> Key: HDFS-5153
> URL: https://issues.apache.org/jira/browse/HDFS-5153
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: datanode
> Affects Versions: 3.0.0
> Reporter: Arpit Agarwal
>
> When the number of blocks on the DataNode grows large we start running into a
> few issues:
> # Block reports take a long time to process on the NameNode. In testing we
> have seen that a block report with 6 Million blocks takes close to one second
> to process on the NameNode. The NameSystem write lock is held during this
> time.
> # We start hitting the default protobuf message limit of 64MB somewhere
> around 10 Million blocks. While we can increase the message size limit it
> already takes over 7 seconds to serialize/unserialize a block report of this
> size.
> HDFS-2832 has introduced the concept of a DataNode as a collection of
> storages i.e. the NameNode is aware of all the volumes attached to a given
> DataNode. this makes it easy to split block reports from the DN by sending
> one report per attached storage.
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