For the same reasons that "Replica" shouldnt be called "Replica" (it
requires to long an explanation to agree that it is an ok name),
"replicationFactor" shouldnt be called "replicationFactor" and long as
it referes to the TOTAL number of cores you get for your "Shard".
"replicationFactor" would be an ok name if replicationFactor=0 meant one
core, replicationFactor=1 meant two cores etc., but as long as
replicationFactor=1 means one core, replicationFactor=2 means two cores,
it is bad naming (you will not get any replication with
replicationFactor=1 - WTF!?!?). If we want to insist that you specify
the total number of cores at least use "replicaPerShard" instead of
"replicationFactor", or even better rename "Replica" to "Shard-instance"
and use "instancesPerShard" instead of "replicationFactor".
Regards, Per Steffensen
On 1/3/13 3:52 PM, Per Steffensen wrote:
Hi
Here is my version - do not believe the explanations have been very clear
We have the following concepts (here I will try to explain what each
the concept cover without naming it - its hard)
1) Machines (virtual or physical) running Solr server JVMs (one
machine can run several Solr server JVMs if you like)
2) Solr server JVMs
3) Logical "stores" where you can add/update/delete data-instances
(closest to "logical" tables in RDBMS)
4) Logical "slices" of a store (closest to non-overlapping "logical"
sets of rows for the "logical" table in a RDBMS)
5) Physical instances of "slices" (a physical (disk/memory) instance
of the a "logical" slice). This is where data actually goes on disk -
the logical "stores" and "slices" above are just non-physical concepts
Terminology
1) Believe we have no name for this (except of course machine :-) ),
even though Jack claims that this is called a "node". Maybe sometimes
it is called a "node", but I believe "node" is more often used to
refer to a "Solr server JVM".
2) "Node"
3) "Collection"
4) "Shard". Used to be called "Slice" but I believe now it is
officially called "Shard". I agree with that change, because I believe
most of the industry also uses the term "Shard" for this
logical/non-physical concept - just needs to be reflected it across
documentation and code
5) "Replica". Used to be called "Shard" but I believe now it is
officially called "Replica". I certainly do not agree with the name
"Replica", because it suggests that it is a copy of an "original", but
it isnt. I would prefer "Shard-instance" here, to avoid the confusion.
I understand that you can argue (if you argue long enough) that
"Replica" is a fine name, but you really need the explanation to
understand why "Replica" can be defended as the name for this. Is is
not immediately obvious what this is as long as it is called
"Replica". A "Replica" is basically a Solr Cloud managed Core and
behind every Replica/Core lives a physical Lucene index. So
Replica=Core) contains/maintains Lucene index behind the scenes. The
term "Replica" also needs to be reflected across documentation and code.
Regards, Per Steffensen
