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https://issues.apache.org/jira/browse/HDFS-5682?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14008153#comment-14008153
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Zesheng Wu commented on HDFS-5682:
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I read through the API doc, its really very clear:) Following are some minor
suggestions:
1. About the storage type, because I didn't participate the discussion in
HDFS-2832, I am confused by the current storage type DISK and SSD. I think SSD
is also one type of disk, DISK and SSD are not orthogonal. Can we change
storage type to HDD and SDD, this will be more straightforward?
2. About setStorageTypeSpaceQuota/getStorageTypeSpaceQuota, these two names are
not very natural. From the literal meaning, it sounds like setting/getting
space quota on some storage type other than some type of storage. I would
suggest that setStorageSpaceQuota/getStorageSpaceQuota will be better. I am not
a native English speaker, if I were wrong, just ignore this.
3. About the command line, hdfs dfsadmin -get(set)StorageTypeSpaceQuota, I
think get(set) one storage type once is simple and straightforward, if we
get(set) more than one once, because there's no atomicity guarantee, it's
complicated to handle failure.
4. About the StoragePreference class, as you said in the design doc in
HDFS-2832, in the future HDFS will support place replicas on different
storages, such as 1 on SSD, and 2 on HDD. I would suggest that
StoragePerference class can support specifying storage type of each replica
now, in this way, we can easily support the above feature in the future.
5. About the create file sematics, as you said in the doc "During file creation
there must be sufficient quota to place at least one block times the
replication factor on the target storage type, otherwise the request is falied
immediately with QuotaExceededException", I think it will be more natural and
friendly that first create the file on the default storage(HDD) if there's not
enough space of desired storage type , and than let the namenode replicate the
block to desired storage lazily when there's enough space available.
> Heterogeneous Storage phase 2 - APIs to expose Storage Types
> ------------------------------------------------------------
>
> Key: HDFS-5682
> URL: https://issues.apache.org/jira/browse/HDFS-5682
> Project: Hadoop HDFS
> Issue Type: Bug
> Affects Versions: 3.0.0
> Reporter: Arpit Agarwal
> Assignee: Arpit Agarwal
> Attachments: 20140522-Heterogeneous-Storages-API.pdf
>
>
> Phase 1 (HDFS-2832) added support to present the DataNode as a collection of
> discrete storages of different types.
> This Jira is to track phase 2 of the Heterogeneous Storage work which
> involves exposing Storage Types to applications and adding Quota Management
> support for administrators.
> This phase will also include tools support for administrators/users.
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