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From Bill Graham <billgra...@gmail.com>
Subject Re: Questions about HBase Cluster Replication
Date Thu, 03 Mar 2011 17:10:30 GMT
Actually, how far behind replication is w.r.t. edit logs is different
than how out of sync they are, but you get the idea.

On Thu, Mar 3, 2011 at 9:07 AM, Bill Graham <billgraham@gmail.com> wrote:
> One more question for the FAQ:
> 6. Is it possible for an admin to tell just how out of sync the two
> clusters are? Something like Seconds_Behind_Master in MySQL's SHOW
> On Wed, Mar 2, 2011 at 9:32 PM, Jean-Daniel Cryans <jdcryans@apache.org> wrote:
>> Although, I would add that this feature is still experimental so who knows :)
>> I think the worst that happened to us was that replication was broken
>> (see the jira where if the master loses it's zk session with the slave
>> zk ensemble, it requires a HBase restart on the master side) for a few
>> days because of maintenance of the link between the two datacenters
>> which took more than a minute. When we finally did restart the master
>> cluster, it had to process about 2TBs of HLogs... those ICVs can
>> really generate a lot of data!
>> J-D
>> On Wed, Mar 2, 2011 at 9:25 PM, Jean-Daniel Cryans <jdcryans@apache.org> wrote:
>>>> 5. If one is adding replication on the *production* Master cluster, what's
>>>> worst thing that can happen to this Master cluster?  Nothing scary other
>>>> changing configs + interruption during a restart? (which is currently still
>>>> because of region assignments?)
>>> The replication code is pretty much encapsulated from the rest of the
>>> region server code, it won't mess with your Puts or change your
>>> birthday date.
>>> With 0.90 the regions are reassigned where they were before, so it's
>>> really just the block cache that gets screwed.
>>> J-D

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