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From Shawn Heisey <apa...@elyograg.org>
Subject Re: ZooKeeper in different datacenters
Date Wed, 22 Aug 2018 19:54:21 GMT
On 8/22/2018 11:10 AM, ilango dhandapani wrote:
> So, if I have 3 zk servers on 1st DC, 2 solr servers on 1st DC and 2 solr
> servers on 2nd DC, this will work right ? Other than network/latency between
> DC1 and DC2 for solr replication.

No.  This is what I was trying to tell you.

With half your ZK servers in one DC and half in the other, if you lose 
either datacenter, ZK loses quorum, and SolrCloud switches to 
read-only.  If you still have a complete copy of your indexes, you'll be 
able to continue making queries, but you will be unable to make any 
changes to any index until the datacenter comes back up.  When there are 
six ZK servers, you must have at least four of them operational and 
reachable, or you do not have quorum.

For fault tolerance on ZK, you need at least three data centers.  So 
that if you lose any datacenter, quorum can still be maintained with the 
ZK servers in the other two datacenters.


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