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From Shawn Heisey <>
Subject Re: cores vs. instances vs. zookeeper vs. cloud vs ?
Date Fri, 16 Dec 2016 20:31:54 GMT
On 12/16/2016 10:30 AM, John Blythe wrote:
> thanks, erick. this is helpful. a few questions for clarity's sake, but
> first: nope, not using SolrCloud as of yet.
>    - if i start using SolrCloud i could have my current multi-core setup
>    (e.g. "transactions", "opportunities", etc.) exist within the appropriate
>    collection. so instead of dev-transactions i'd have a 'dev' collection that
>    has a 'transactions' core inside of it?

No.  You would not be thinking in terms of cores at all.  When your
programs talk to SolrCloud, they will only care about collections.

Some terminology clarification: Collections are made up of one or more
shards.  Shards are made up of one or more replicas.  Each shard replica
is a core.  One replica for each shard is elected as leader.  If there's
only one replica, then there's no redundancy, and that replica becomes

For the example you gave, you would have dev-transactions and
prod-transactions collections.  Each of these collections might have
shard replicas (cores) on completely different machines in the cloud ...
or they might be on the same machines.  During normal operation, you
would never access a core directly.  You'd probably only ever do that if
something went very wrong and you needed to take very unusual steps to
fix it or figure out what went wrong.

>    - this seems to be the same with ZK, too?

No idea what you're asking here.  Perhaps it should be obvious, but I
can't figure it out.

>    - i'm totally fine w separate/diff indexing. the demo collection, for
>    instance, *has* to be separate from production bc the data has been
>    stitched together from various customers' accounts on prod and blinded so
>    that we have avoid privacy issues and can have all the various goodies
>    under one demo account rather than separate ones. is the separate indexing
>    happening out of the box w Cloud or something it's even capable of?

Again, I don't really know what you're asking with "separate indexing". 
Different collections are separate from each other, just like cores in
standalone mode.  Each collection is linked to a configuration in
Zookeeper, which all of its shard replicas (cores) will use.  You could
have all your collections pointing to the same config.  Some (or all) of
them could point to completely different configs, too.

Addressing a later question:  You don't have SolrCloud if you don't have
zookeeper.  ZK is a requirement.  You don't really interact directly
with zookeeper when you're using SolrCloud.  It's an administrative
detail in the *setup* of SolrCloud.


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