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From Ask Bjørn Hansen <>
Subject Re: Largest CouchDB dbs?
Date Sun, 09 Nov 2008 06:55:37 GMT

On Nov 3, 2008, at 1:34, Jan Lehnardt wrote:

> Another part is the Erlang to JSON conversion that is known to be  
> slow-ish. I don't know which side of the conversion weighs more  
> though. We are working with the Erlang community and developers to  
> get a C-based JSON encoder into Erlang. Since building a view server  
> is relatively straightforward, giving a Perl version a shot is  
> probably worth it.

You are right that it's the Erlang side that's slow.   beam.smp uses  
~100% CPU while couchjs just uses 10-15% (depending on the complexity  
of the map function).

Even just inserting documents (a few KB each) is going sloowly.   
Inserting 2000 new documents is taking about 12 seconds on 2.5GHz of  
whatever Intel's new server CPUs are called.

Is that right?  I'm using SVN as of a few days ago.

(RAID 10 on 14 15k SAS disks, many more GB ram than the dataset etc -  
as far as I can tell the workload is entirely CPU bound - there are 8  
CPU cores, but as I understand it CouchDB basically only uses more  
than one when updating views, and even then it's limited by the main  
process being CPU bound).

> Which Erlang version are you running. R11B-x is known for causing  
> view-build slowness.
> R12B-3 and R12B-4 are good.

I think I'm using R12B-3.  The RPM I am using is erlang-R12B-3.3.el5.

  - ask

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