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From Stack <st...@duboce.net>
Subject Re: hadoop without append in the absence of puts
Date Thu, 23 Jun 2011 04:38:47 GMT
On Wed, Jun 22, 2011 at 7:09 PM, Andrew Purtell <apurtell@apache.org> wrote:
>> From: Andreas Neumann <neunand@gmail.com>
>
>> I guess that includes region splits but also
>> reassignment of a region after its region server died.
>
> If you are not writing, then you won't see splits.
>

You can also disable splits.


> Reassignment does involve writes to META but missing these is less serious than missing
a change in table structure. Stack could say more here but I believe the Master will discover
inconsistency and repair it.
>

Not really  In 0.20.x we had a thread that did fixup on .META. by
scanning it on a period and it notice if a region was assigned to a
regionserver that was no longer registered but we don't really do that
any more.  If it turns out you have a problem in here Andreas, you
could run the .META. checker externally and if an inconsistency, its
easy enough forcing region reassign.


> HBase can do the (near) equivalent of this without requiring any code changes. Set hbase.regionserver.logroll.period
to an insanely low value.
>

As Andy says, this would be S L O W but your write rate might be low
enough -- only .META. edits -- it might be work (set log roll in the
kbs rather than mbs).

St.Ack

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