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From "Jesse Yates (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-6180) [brainstorm] Timestamp based snapshots in HBase 0.96
Date Mon, 18 Jun 2012 17:23:42 GMT

    [ https://issues.apache.org/jira/browse/HBASE-6180?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13396047#comment-13396047
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Jesse Yates commented on HBASE-6180:
------------------------------------

Further recommendation for the timestamp based, swapping memstore/flush approach - distributed
splits cause the WALs to be moved to another directory, causing our symlinks (via the Reference
class) to become invalid. This isn't a problem if we have hardlinks, but as they aren't implemented
yet and will probably take a lot work to back-port to HDFS-1.0, we should probably just ignore
that solution. 

I'm not convinced that the WAL edit approach that it would be any faster to take the snapshot.
Further, using the WAL actually makes the restore much more complicated as you need to replay
WAL files to get back to the table state - a big pain for a restoring to a read only table
and generally just adding a lot of lag when you could just hook-up a bunch of immutable files.
                
> [brainstorm] Timestamp based snapshots in HBase 0.96
> ----------------------------------------------------
>
>                 Key: HBASE-6180
>                 URL: https://issues.apache.org/jira/browse/HBASE-6180
>             Project: HBase
>          Issue Type: Brainstorming
>            Reporter: Jesse Yates
>             Fix For: 0.96.0
>
>
> Discussion ticket around doing timestamp based snapshots in HBase as an extension/follow-on
work for HBASE-6055. The implementation in HBASE-6055 (as originally defined) is not sufficient
for real-time clusters because it requires downtime to take the snapshot. 
> Time-stamp based snapshots should not require downtime at the cost of achieving global
consistency. 

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