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HBase, mail # user - WAL corruption


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Re: WAL corruption
Jerry Lam 2012-07-02, 17:45
my understanding is that the WAL log is used for replication as well.
If all your data has been persisted to disk (i.e. all data in memstores have been flushed to disks) and replication is disabled, I believe you can delete the WAL without data loss.

just my 2 cents

On 2012-07-02, at 1:37 PM, Bryan Keller wrote:

> During an upgrade of my cluster to 0.90 to 0.92 over the weekend, the WAL (files in the /hbase/.logs directory) was corrupted and it prevented HBase from starting up. The exact exception was "java.io.IOException: Could not obtain the last block locations" on the WAL files.
>
> I was able to recover by deleting the /hbase/.logs directory. My question is, if HBase had no pending updates, i.e. nothing writing to it, is there any risk of data loss by deleting the WAL directory? For example, does rebalancing, flushing, or compaction use the WAL or is the WAL used only for inserts/updates/deletes?