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From "Kai Zheng (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-7240) Object store in HDFS
Date Mon, 13 Jun 2016 21:05:04 GMT

    [ https://issues.apache.org/jira/browse/HDFS-7240?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15328259#comment-15328259

Kai Zheng commented on HDFS-7240:

Thanks all for the discussion and [~anu] for this nice summary.

bq. To support Erasure coding, SCM will have to return more than 3 machines, let us say we
were using 6 + 3 model of erasure coding then then a container is spread across nine machines.
Once we modify SCM to support this model, the container client will have write data to the
locations and update the RAFT state with the metadata of this block.
This looks like to support the striping erasure coding in client when putting/updating a k/v
to the store, right? For small objects, the write will trigger the relatively expensive work
of coding and writing to 6+3 locations, I would doubt about the performance/overhead and the
benefit. For large objects, it sounds fine. So like we did for striping files, users should
also be able to opt striping or not according to their bucket conditions, I guess.

In HDFS files, in addition to striping, there is another way to do erasure coding in block
level as discussed in HDFS-8030, mainly targeting to convert old/cold data from replica into
erasure coded for saving storage. In Ozone, how about this approach? Would we have old/cold
buckets that can  be frozen and no update any longer? I'm not sure about this from users'
point of view, but we might not reuse the same sets of buckets/containers across many years,

> Object store in HDFS
> --------------------
>                 Key: HDFS-7240
>                 URL: https://issues.apache.org/jira/browse/HDFS-7240
>             Project: Hadoop HDFS
>          Issue Type: New Feature
>            Reporter: Jitendra Nath Pandey
>            Assignee: Jitendra Nath Pandey
>         Attachments: Ozone-architecture-v1.pdf, Ozonedesignupdate.pdf, ozone_user_v0.pdf
> This jira proposes to add object store capabilities into HDFS. 
> As part of the federation work (HDFS-1052) we separated block storage as a generic storage
layer. Using the Block Pool abstraction, new kinds of namespaces can be built on top of the
storage layer i.e. datanodes.
> In this jira I will explore building an object store using the datanode storage, but
independent of namespace metadata.
> I will soon update with a detailed design document.

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