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https://issues.apache.org/jira/browse/HDFS-2832?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13813495#comment-13813495
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Konstantin Shvachko commented on HDFS-2832:
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Hey guys, I was wondering if we really need to change storageID to UUID. I
thought that the storageID approach that _each DN is able to generate a unique
id independently of the others_ is a good feature to retain. UUID as you noted
is not unique and needs to be coordinated through NameNode.
I understand you have multiple storages on the same DN, and you need unique ids
independently of the ip, and port.
# They should be unique with existing implementation of
{{createNewStorageId()}}.
{code}storageid = <random, ip, port, currentTime>{code}
If you generate ids sequentially one after another, currentTime should be
different. It can be replaced by nano-time if id generation is done in
different threads.
# You can also add to storageID an attribute that characterizes the disk volume
or the directory as a new component. Examples of the new attribute could be
disk serial number, or the storage directory inode number.
It seems that introduction of UUIDs was unnecessary, unless of course I missed
some context.
> Enable support for heterogeneous storages in HDFS
> -------------------------------------------------
>
> Key: HDFS-2832
> URL: https://issues.apache.org/jira/browse/HDFS-2832
> Project: Hadoop HDFS
> Issue Type: New Feature
> Affects Versions: 0.24.0
> Reporter: Suresh Srinivas
> Assignee: Suresh Srinivas
> Attachments: 20130813-HeterogeneousStorage.pdf, h2832_20131023.patch,
> h2832_20131023b.patch, h2832_20131025.patch, h2832_20131028.patch,
> h2832_20131028b.patch, h2832_20131029.patch, h2832_20131103.patch
>
>
> HDFS currently supports configuration where storages are a list of
> directories. Typically each of these directories correspond to a volume with
> its own file system. All these directories are homogeneous and therefore
> identified as a single storage at the namenode. I propose, change to the
> current model where Datanode * is a * storage, to Datanode * is a collection
> * of strorages.
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