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https://issues.apache.org/jira/browse/HBASE-50?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12855824#action_12855824
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Li Chongxin commented on HBASE-50:
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@Todd Lipcon
bq. This is the part I'm not clear on. Are you attempting to achieve a
simultaneous write lock across all region servers in the cluster? Also will
have to make sure that we "lock" any regions that are currently being moved,
etc. Doing this without impacting realtime workload on the cluster is the
tricky part in my opinion.
Sorry for the mistake that rather than write lock, a read lock instead should
be acquired when the snapshot is requested. So this read lock will only block
the regions that are currently being moved and other operations such as Get,
Put, Delete etc are not impacted at all. Also this lock is not held across all
region servers but only per region. A Region is locked only when we dump the
manifest of the region and other regions will not be affected. I think this
process is pretty quick and will not impact the whole cluster a lot.
bq. Hard links would make it easier, but in a large cluster with thousands of
regions each with many hfiles and many column families, iterating over every
store file could be prohibitively expensive if we have to lock everything while
doing it.
Yes, totally agree with you. Iterating over stored files is not efficient.
That's why I want to find some other mechanism to manage the reference counting
problem. Probably via .META. data or Zookeeper, I still don't have a concrete
solution, any good ideas?
> Snapshot of table
> -----------------
>
> Key: HBASE-50
> URL: https://issues.apache.org/jira/browse/HBASE-50
> Project: Hadoop HBase
> Issue Type: New Feature
> Reporter: Billy Pearson
> Priority: Minor
>
> 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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