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From Benoit Chesneau <>
Subject database design question: concurrent writes
Date Thu, 13 Dec 2012 16:06:59 GMT
Hi all,

This morning I was back reading a lot of fundamentals about  databases and
such and was asking myself how we could increase the number of concurrent

These days the theory is that it will be solved by sharding the databases
in multiples database files and merging results of the queries. Since the
databases will be shareded then the writes on the same db will be
concurrents. A map of the shards willl be kept aside. All of this thanks to
the introduction of bigcouch.

The question I have is why don't we already do that? Ie balancing datas on
different files on one db? for example the db folder could be


where XY are the first letters of an id or content hash or any consistent
hashing method.

I am currently asking myself such question because I am wondering how will
the backup works when couchdb will be used as a single node. How to backup
only one db without having to query for the mapping and such? How to keep
it it simple.

Related to that why did bigcouch used that design? Why mapping shards in a
db database instead of having some kind of natural balancing on the fs and
having a consistent hashing algorithm used to balance on different
machines/vms as well ?

- benoƮt

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