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From "Billy" <sa...@pearsonwholesale.com>
Subject Re: Question for HBase users
Date Fri, 04 Jan 2008 07:00:59 GMT
Saying that the working release only came out 3 months ago I would hope no 
one had data stored in hbase at this time that is not backup and/or stored 
somewhere else. so that puts me at a -1 on the migration utility. but I 
might be wrong above most if using hbase they should be able to output the 
data to a flat file in hadoop to be imported later after the update.

Billy


"Jim Kellerman" <jim@powerset.com> wrote in 
message 
news:84E2AE771361E9419DD0EFBD31F09C4D4C8C3379F1@EXVMBX015-1.exch015.msoutlookonline.net...
Do you have data stored in HBase that you cannot recreate?

HADOOP-2478 will introduce an incompatible change in how HBase
lays out files in HDFS so that should the root or meta tables
be corrupted, it will be possible to reconstruct them from
information in the file system alone.

The problem is in building a migration utility. Anything that
we could build to migrate from the current file structure to
the new file structure would require that the root an meta
regions be absolutely correct. If they are not, the migration
would fail, because there is not enough information on disk
currently to rebuild the root and meta regions.

Is it acceptable for this change to be made without the provision
of an upgrade utility?

If not, are you willing to accept the risk that the upgrade
may fail if you have corruption in your root or meta regions?

After HADOOP-2478, we will be able to build a fault tolerant
upgrade utility, should HBase's file structure change again.
Additionally, we will be able to provide the equivalent of
fsck for HBase after HADOOP-2478.

---
Jim Kellerman, Senior Engineer; Powerset

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