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https://issues.apache.org/jira/browse/HBASE-50?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12896989#action_12896989
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HBase Review Board commented on HBASE-50:
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Made a start. More to follow.
src/main/java/org/apache/hadoop/hbase/HConstants.java
<http://review.cloudera.org/r/467/#comment2706>
Is this what I think it is? We are keeping reference counts on a region up
in .META.? What about the question I had a while back on what happens when
this row is deleted because the region has split and daughters no longer have
reference to this parent? Maybe this is something else. I'll keep reading.
src/main/java/org/apache/hadoop/hbase/HConstants.java
<http://review.cloudera.org/r/467/#comment2708>
ok.. I think I see whats going to happen (perhaps ignore previous comment)
src/main/java/org/apache/hadoop/hbase/HRegionInfo.java
<http://review.cloudera.org/r/467/#comment2709>
How often is this called? If it happens alot, it could add up -- be
expensive.
src/main/java/org/apache/hadoop/hbase/HRegionInfo.java
<http://review.cloudera.org/r/467/#comment2710>
Ok. Good.
src/main/java/org/apache/hadoop/hbase/HSnapshotDescriptor.java
<http://review.cloudera.org/r/467/#comment2711>
Drop the H. Call it SnapshotDescriptor
src/main/java/org/apache/hadoop/hbase/HSnapshotDescriptor.java
<http://review.cloudera.org/r/467/#comment2712>
If it is in under the snapshot directory maybe just call this file
snapshotinfo? Drop the '.' prefix. The '.' prefix is usually to demark
'special' files we don't want to consider as part of normal operation. In this
case, we are under a snapshot directory, already outside of 'normal' operation.
- stack
> Snapshot of table
> -----------------
>
> Key: HBASE-50
> URL: https://issues.apache.org/jira/browse/HBASE-50
> Project: HBase
> Issue Type: New Feature
> Reporter: Billy Pearson
> Assignee: Li Chongxin
> Priority: Minor
> Attachments: HBase Snapshot Design Report V2.pdf, HBase Snapshot
> Design Report V3.pdf, HBase Snapshot Implementation Plan.pdf, Snapshot Class
> Diagram.png
>
>
> Havening an option to take a snapshot of a table would be vary useful in
> production.
> What I would like to see this option do is do a merge of all the data into
> one or more files stored in the same folder on the dfs. This way we could
> save data in case of a software bug in hadoop or user code.
> The other advantage would be to be able to export a table to multi locations.
> Say I had a read_only table that must be online. I could take a snapshot of
> it when needed and export it to a separate data center and have it loaded
> there and then i would have it online at multi data centers for load
> balancing and failover.
> I understand that hadoop takes the need out of havening backup to protect
> from failed servers, but this does not protect use from software bugs that
> might delete or alter data in ways we did not plan. We should have a way we
> can roll back a dataset.
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