[
https://issues.apache.org/jira/browse/HDFS-2576?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13589228#comment-13589228
]
Uma Maheswara Rao G commented on HDFS-2576:
-------------------------------------------
{quote}
>From a design point of view would it be possible to just add an attribute or
>flag on hdfs files or directories that specify an block affinity group? This
>would seem cheaper than an alternative that specifies specific favored dn's
>lists for block replicas. This would seem more robust than something specified
>only at file creation time, and more managable in the long term if data nodes
>membership changes over time.
{quote}
+1
Also looks like this idea is closure to
http://www.vldb.org/pvldb/vol4/p575-eltabakh.pdf (cohadoop)
Anyway HDFS take care of keeping first block local to the node.(is that the
case like one RS create the files, another RS will work on them? not sure is
there a case ). Once HDFS choosen the targets for first block, subsequent block
can use the same location as previous block? I am not sure what is the Strict
requirement of passing node addresses from client. Even if further files also
wanted to choose the same targets, we can pass same group id then the blocks
for that file also will be placed in same nodes. This looks to be generic
idea. Persisting thism will help HDFS balancers to replicate if DN alone goes
down for the replication. I might miss lot of history in this discussion,
please correct me if I am wrong.
Also, most of the required new target choosing mechanism should go as new
pluggable policy.[may be required api can be added to policy interface to fit
this requirement]
> Namenode should have a favored nodes hint to enable clients to have control
> over block placement.
> -------------------------------------------------------------------------------------------------
>
> Key: HDFS-2576
> URL: https://issues.apache.org/jira/browse/HDFS-2576
> Project: Hadoop HDFS
> Issue Type: New Feature
> Reporter: Pritam Damania
> Attachments: hdfs-2576-1.txt
>
>
> Sometimes Clients like HBase are required to dynamically compute the
> datanodes it wishes to place the blocks for a file for higher level of
> locality. For this purpose there is a need of a way to give the Namenode a
> hint in terms of a favoredNodes parameter about the locations where the
> client wants to put each block. The proposed solution is a favored nodes
> parameter in the addBlock() method and in the create() file method to enable
> the clients to give the hints to the NameNode about the locations of each
> replica of the block. Note that this would be just a hint and finally the
> NameNode would look at disk usage, datanode load etc. and decide whether it
> can respect the hints or not.
--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators
For more information on JIRA, see: http://www.atlassian.com/software/jira
