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https://issues.apache.org/jira/browse/HDFS-11154?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15684815#comment-15684815
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Chen Liang commented on HDFS-11154:
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Thanks [~anu] for the comments!
bq. 1. Wondering if we need a lock in CBlockManager.java between the calls.
The operations calling into {{StorageManager}} are already syncd on
{{StorageManager}}'s own lock. The next patch will include locks for those
operations on the levelDB instance.
bq. 2. For function testSame, did you want to implement a Comparable interface ?
I'm under the impression that {{Comparable}} is more to support sorting a list
of object, the {{compareTo()}} returns an int value indicating an relative
order, and I assumed it is not supposed to be called directly (please correct
me if I'm wrong though). Probably overriding {{equals}} is making more sense
but it requires implementing hashcode also. Since this is only a simple method
for testing, I decided not to go with a potentially confusing way. What do you
think?
bq. 3. Why are we copying the levelDB store class ? Can we move this to a place
where both Ozone and Cblock can use it instead of having 2 copies of the same
class ?
Simply because I assumed the use of levelDB is only temporary and at the end of
the day we will switch to RAFT (which I suppose is the same for Ozone). Plus i
was trying to not to make any change to Ozone code base.
> Block Storage : store server state to persistent storage
> --------------------------------------------------------
>
> Key: HDFS-11154
> URL: https://issues.apache.org/jira/browse/HDFS-11154
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: hdfs
> Reporter: Chen Liang
> Assignee: Chen Liang
> Attachments: HDFS-11154-HDFS-7240.001.patch,
> HDFS-11154-HDFS-7240.002.patch, HDFS-11154-HDFS-7240.003.patch
>
>
> Currently, all the storage state are kept in server memory. If server
> crashes, we would lose all the volume information. This JIRA stores server
> internal state into its local disk. Such that on server failure, we can
> simply restart server and restore volume information from disk.
> More specifically, the internal state written to disk is mainly the mapping
> from volume to its underlying containers, plus some meta information such as
> volume size, block size, etc.
> Note that this is only a simple, minimum set mechanism for persistence. It is
> more like a counterpart of fsimage in HDFS, but without edit logs.
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