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From Nicolas Spiegelberg <nspiegelb...@fb.com>
Subject Re: hbase 0.94.0
Date Fri, 03 Feb 2012 01:24:20 GMT
>>I think HFile upgrade in particular is more complicated than you think.
>>We currently have production traffic running with HFileV1.  It has a
>>SLA.  We can't afford to take the entire downtime to rewrite 100GB (or
>>whatever) worth of data.  We need to do this while the cluster is live.
>AFAIK that's how it's done, V1 files are being rewritten to V2 when a
>compaction happens. You don't have to do some offline processing
>before getting the cluster back online.

Correct.  Sorry for the confusion.  I just meant that we shouldn't get rid
of the HFileV1 Reader because it allows online upgrades to happen as
compactions happen.  Trying to remove this functionality or refactor this
to some transformation utility would have negative consequences.  LSMT is
designed with immutability as a core principle, so I think we should
incline towards creating online mutation of persistent data as opposed to
migration utilities.

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