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From "HBASE" <hb...@patientcentral.com>
Subject RE: When does a row become highly available?
Date Fri, 11 Dec 2009 19:08:42 GMT
Also, as I recall one may set the replication factor both when
1. creating the table
2. inserting data

Anyone please correct me if I'm incorrect.

I set things up before, added a new server, and noticed that existing tables didn't automatically
update the replication factor to the new dfs.replication after I restarted everything. I ran
the following command to correct it:

bin/hadoop dfs -setrep -R -w 3 /
(sets to replication factor of three for everything under the / in HDFS)

HTH
-Matt Davies

-----Original Message-----
From: HBASE [mailto:hbase@patientcentral.com] 
Sent: Friday, December 11, 2009 11:59 AM
To: hbase-user@hadoop.apache.org
Subject: RE: When does a row become highly available?

Seth,

Have you updated the default dfs.replication from 1 to some other value?

Best,
Matt Davies

-----Original Message-----
From: Seth Ladd [mailto:sethladd@gmail.com] 
Sent: Friday, December 11, 2009 11:55 AM
To: hbase-user@hadoop.apache.org
Subject: Re: When does a row become highly available?

>> Which confuses me, if the write goes straight to a RegionServer, but
>> then the RegionServer fails before the MemStore is flushed, did I just
>> lose data?
>
> No that's the goal of the write-ahead-log (WAL).

Here's the scenario I just tested on my EC2 cluster.  3 Zookeeper
instances, 1 master, and 3 slaves.

I created a table, and inserted a single row.
I performed a read (get) to test the insert, and sure enough the row
was returned.
I then noted which slave held the table, and terminated the slave via
the AWS management console.
I then waited approx 30 seconds.
I used the web interfaces (port 60030 and 60010) to note that the
region was indeed moved to another slave.
I performed a read on the same row, but did *not* find the row.

So it looks like the region for the table was moved, but no data was moved over.

Was that a valid test?  I would expect the row to get moved with the region.

Thanks,
Seth


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