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From "Rakesh R (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-10285) Storage Policy Satisfier in Namenode
Date Wed, 02 Aug 2017 12:46:01 GMT

    [ https://issues.apache.org/jira/browse/HDFS-10285?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16110815#comment-16110815
] 

Rakesh R commented on HDFS-10285:
---------------------------------

Thanks [~xiaochen] for the interests. Below is the response, please take a look at it.
bq. In FSDirSatisfyStoragePolicyOp, we keep a temporary list of INodes candidateNodes
Good catch! HDFS-12225 has already raised to optimize the extended attributes and your point
will be taken care as part this jira changes.
bq. The new removeXattr method in FSN appears to be not audit logged.
Since remove xattr is an internal operation and avoided audit logging.
bq. BlockManager, haEnabled is added.  But currently other places in the same class checks
that from config. 
I will incorporate this changes in HDFS-12214 jira
bq. BlockManager, if (storagePolicyEnabled && spsEnabled) == false, we print a WARN
log
 I will reduce the log priority to DEBUG. I will incorporate this changes in HDFS-12214 jira.

> Storage Policy Satisfier in Namenode
> ------------------------------------
>
>                 Key: HDFS-10285
>                 URL: https://issues.apache.org/jira/browse/HDFS-10285
>             Project: Hadoop HDFS
>          Issue Type: New Feature
>          Components: datanode, namenode
>    Affects Versions: HDFS-10285
>            Reporter: Uma Maheswara Rao G
>            Assignee: Uma Maheswara Rao G
>         Attachments: HDFS-10285-consolidated-merge-patch-00.patch, HDFS-10285-consolidated-merge-patch-01.patch,
HDFS-SPS-TestReport-20170708.pdf, Storage-Policy-Satisfier-in-HDFS-June-20-2017.pdf, Storage-Policy-Satisfier-in-HDFS-May10.pdf
>
>
> Heterogeneous storage in HDFS introduced the concept of storage policy. These policies
can be set on directory/file to specify the user preference, where to store the physical block.
When user set the storage policy before writing data, then the blocks could take advantage
of storage policy preferences and stores physical block accordingly. 
> If user set the storage policy after writing and completing the file, then the blocks
would have been written with default storage policy (nothing but DISK). User has to run the
‘Mover tool’ explicitly by specifying all such file names as a list. In some distributed
system scenarios (ex: HBase) it would be difficult to collect all the files and run the tool
as different nodes can write files separately and file can have different paths.
> Another scenarios is, when user rename the files from one effected storage policy file
(inherited policy from parent directory) to another storage policy effected directory, it
will not copy inherited storage policy from source. So it will take effect from destination
file/dir parent storage policy. This rename operation is just a metadata change in Namenode.
The physical blocks still remain with source storage policy.
> So, Tracking all such business logic based file names could be difficult for admins from
distributed nodes(ex: region servers) and running the Mover tool. 
> Here the proposal is to provide an API from Namenode itself for trigger the storage policy
satisfaction. A Daemon thread inside Namenode should track such calls and process to DN as
movement commands. 
> Will post the detailed design thoughts document soon. 



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