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https://issues.apache.org/jira/browse/HDFS-2733?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13201160#comment-13201160
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Eli Collins commented on HDFS-2733:
-----------------------------------
Looks good. Comments follow.
* Might make sense to use machine and host consistently (maybe pick one).
* In the "option of running two redundant NameNodes" paragraph would mention
that we now "support an Active/Passive configuration with a hot standby" since
that's the standard HA description for our configuration.
* Perhaps be explicit that there are two types of state, persistent and
ephemeral state. That all persistent state modifications and some emphemeral
(eg block allocation) are logged, with the remaining ephemeral state (block
reports) are handled by the Datanodes communicating two both Namenodes.
* Might be worth mentioning that we fence both with the fencers but the NNs
also fence operations outside the edits log (eg operations from block reports)
* In the NFS server section, technically there's no requirement it be an NFS
server. Would mention that the availability of the system is limited by the
availability of the shared edits dir, therefore in order to remove all single
points of failure there needs to be redundancy for the shared edits dir.
Specifically, multiple network paths to the storage, and redundancy in the
storage itself (disk, network and power).
* Perhaps mention that today manual failover is supported and automatic
failover is coming?
* Can mention explicitly that the NN/SBN layout allows people to re-use their
existing 2NN/SBN hardware configuration.
* s/any change/change/
* Wrt syncing metadata directories, perhaps worth noting that you only need to
sync the edits directory since the shared edits dir only contains edits (people
may be confused why the old image they copied there never gets updated)
* Should mention that checkHealth currently doesn't do anything
> Document HA configuration and CLI
> ---------------------------------
>
> Key: HDFS-2733
> URL: https://issues.apache.org/jira/browse/HDFS-2733
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: documentation, ha
> Affects Versions: HA branch (HDFS-1623)
> Reporter: Eli Collins
> Assignee: Aaron T. Myers
> Attachments: HDFS-2733-HDFS-1623.patch, HDFS-2733-HDFS-1623.patch,
> HDFSHighAvailability.html, HDFSHighAvailability.html
>
>
> We need to document the configuration changes in HDFS-2231 and the new CLI
> introduced by HADOOP-7774.
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