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From "Colin Patrick McCabe (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-5442) Zero loss HDFS data replication for multiple datacenters
Date Thu, 06 Mar 2014 23:46:45 GMT

    [ https://issues.apache.org/jira/browse/HDFS-5442?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13923265#comment-13923265
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Colin Patrick McCabe commented on HDFS-5442:
--------------------------------------------

Log-shipping is implemented by many databases, including all the popular open-source databases
such as Postgres and MySQL.  However, HDFS is not a database and doesn't have physio-logical
logs in the same sense as those projects.

What we do have is blocks, which have to be replicated in both places, and of course the edits.
 Check out the part of the design doc that deals with MIRROR_DATANODE_AVAILABLE, etc. stuff
to see how the DataNode side of things is handled.

This design also includes the concept of synchronous replication, something I haven't seen
used with MySQL or postgres.

> 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, 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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