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https://issues.apache.org/jira/browse/HDFS-5442?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13852434#comment-13852434
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Jerry Chen commented on HDFS-5442:
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{quote}Along these lines, do the DataNodes in the secondary cluster need to
send block reports to the primary NameNode, or just storage heartbeats?.{quote}
The DataNodes in the secondary cluster will not report or heartbeats to any
NameNodes in the primary cluster in any case. Just like as a normal HDFS
cluster, it will only send block reports or heartbeats to local NameNodes that
in secondary cluster.
{quote}It seems that in the asynchronous case, only the storage report
heartbeats are necessary, in that all the primary NameNode is doing is choosing
secondary DataNodes for inter-datanode DR replication{quote}
In our design, the Active NameNode in secondary cluster will choose the
secondary DataNodes for inter-datanode DR replication and send DR replication
request to NameNode in primary cluster. The Active NameNode in primary cluster
will then choose a source DataNode with the data block and request it to
perform the inter-datanode DR replication.
> Zero loss HDFS data replication for multiple datacenters
> --------------------------------------------------------
>
> Key: HDFS-5442
> URL: https://issues.apache.org/jira/browse/HDFS-5442
> Project: Hadoop HDFS
> Issue Type: Improvement
> Reporter: Avik Dey
> Attachments: Disaster Recovery Solution for Hadoop.pdf
>
>
> Hadoop is architected to operate efficiently at scale for normal hardware
> failures within a datacenter. Hadoop is not designed today to handle
> datacenter failures. Although HDFS is not designed for nor deployed in
> configurations spanning multiple datacenters, replicating data from one
> location to another is common practice for disaster recovery and global
> service availability. There are current solutions available for batch
> replication using data copy/export tools. However, while providing some
> backup capability for HDFS data, they do not provide the capability to
> recover all your HDFS data from a datacenter failure and be up and running
> again with a fully operational Hadoop cluster in another datacenter in a
> matter of minutes. For disaster recovery from a datacenter failure, we should
> provide a fully distributed, zero data loss, low latency, high throughput and
> secure HDFS data replication solution for multiple datacenter setup.
> Design and code for Phase-1 to follow soon.
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