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From Mat Hofschen <hofsc...@gmail.com>
Subject Hbck errors in 0.90.3
Date Wed, 06 Jul 2011 15:22:06 GMT
Hello,

I am wondering what the best way is to fix errors reported with hbck in
0.90.3.
We did a migration from 0.20.4 to 0.90.3 by copying over hbase tables from
0.20.4 to a new cluster with 0.90.3. Then we used add_table.rb to create
META table from scratch. (we stopped all writes to source cluster, flushed
everything, then stopped hbase before copying over).

With hbck there are a few errors (52). Now I am wondering how to fix these.
For example hbck complains about two regions starting with the same key.
Next it complains about 2 regions overlapping. From looking at the META
table there seems to be a "parent region" and two "child regions from a
split". All three regions are registered, producing the two errros.
I examined the old 0.20.4 cluster META table, and it has exactly the same
problem (only there is no hbck to output the error).
So I am assuming that a split on 0.20.4 somehow got into trouble and
produced this error.

How would I go about fixing these problems. I tried to use Merge but got an
NPE.

Also what happens to a write operation that adds a key that would fit into 2
regions. Into which regions is the key actually inserted. Would it pick the
first matching region found in META? Then I am probably in trouble because
all three regions contain valid data.

One more question: How does HBase mark regions as offline in META, for
example if a split has occured but the parent is still not removed?

Thanks for your help.
Matthias

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