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From: Bill Graham <billgraham@gmail.com>
Date: Thu, 3 Mar 2011 09:07:17 -0800
Message-ID: <AANLkTinXQr0cd947pcSHDkfKLhpe-zNx0Wzrh4YDtMka@mail.gmail.com>
Subject: Re: Questions about HBase Cluster Replication
To: user@hbase.apache.org
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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
SLAVE STATUS?


On Wed, Mar 2, 2011 at 9:32 PM, Jean-Daniel Cryans <jdcryans@apache.org> wr=
ote:
> Although, I would add that this feature is still experimental so who know=
s :)
>
> 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, wha=
t's the
>>> worst thing that can happen to this Master cluster? =A0Nothing scary ot=
her than
>>> changing configs + interruption during a restart? (which is currently s=
till bad
>>> 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
>>
>