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https://issues.apache.org/jira/browse/HBASE-50?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12883779#action_12883779
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Li Chongxin commented on HBASE-50:
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bq. isSnapshot in HRI?
bq. Will keeping snapshot data in .META. work? .META. is by region but regions
are deleted after a split but you want your snapshot to live beyond this?
Snapshot data, actually the reference count of hfiles, will be kept in .META.
table, but in a different row than the original region row. So these reference
count information will not be deleted after a split. Reference count
information is saved here because it is also in a region centric view.
Reference count information of a region's hfiles are kept together in a row in
.META. no matter this hfile is still in use or has been archived. I described
this in the Appendix A. of the document.
bq. In zk, writeZnode and readZnode ain't the best names for methods... what
kinda znodes are these? (Jon says these already exist, that they are not your
fault)
Actually the method names for snapshot are startSnapshotOnZK,
abortSnapshotOnZK, registerRSForSnapshot in ZooKeeperWrapper. I put writeZnode
and readZnode in the diagram because I think I can use them inside the above
methods.
Do you think we should make writeZnode and readZnode private and just use them
inside ZooKeeperWrapper?
bq. Can you make a SnapShot class into which encapsulate all related to
snapshotting rather than adding new data members to HMaster? Maybe you do
encapsulate it all into snapshotmonitor?
I haven't figured out all the data members in the design. I will create a
Snapsnot class to encapsulate the related fields if necessary during
implementation.
bq. Can you call RSSnapshotHandler just SnapshotHandler?
sure
bq. You probably don't need to support String overloads.
You mean methods in HBaseAdmin?
A repository has been created in github with the initial content of hbase/trunk
http://github.com/lichongxin/hbase-snapshot
> 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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