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https://issues.apache.org/jira/browse/HBASE-50?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12897735#action_12897735
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HBase Review Board commented on HBASE-50:
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Message from: "Chongxin Li" <[email protected]>
bq. On 2010-08-10 21:34:40, stack wrote:
bq. > src/main/java/org/apache/hadoop/hbase/HTableDescriptor.java, line 673
bq. > <http://review.cloudera.org/r/467/diff/3/?file=6002#file6002line673>
bq. >
bq. > This is fine for an hbase that is a fresh install but what about
case where the data has been migrated from an older hbase version; it won't
have this column family in .META. We should make a little migration script
that adds it or on start of new version, check for it and if not present,
create it.
bq.
bq. Chongxin Li wrote:
bq. That's right. But AddColumn operation requires the table disabled to
proceed, ROOT table can not be disabled once the system is started. Then how
could we execute the migration script or check and create it on start of new
version?
This can be done with a script when HBase is shutdown. The script scans the
root region with MetaUtils and add the column family SNAPSHOT to .META. table?
- Chongxin
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> 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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