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From "Paul Davis" <>
Subject Re: Write Performance
Date Thu, 08 Jan 2009 01:24:35 GMT
Erlang 5.5.5 is borked. 5.6.x should be ok.

Also, yes, writes to the database are serialized in a single thread.
For reference, when storing data, are you using the _bulk_docs

Also, in trunk the fsync calls are turned off by default now so you
should notice more speedup there.

Also, if these are archived records, wouldn't this be a single time
cost? Faster is always better, but if it takes a day, is that a big


On Wed, Jan 7, 2009 at 2:55 PM, Josh Bryan <> wrote:
> Chris Anderson wrote:
>> On Wed, Jan 7, 2009 at 4:37 PM, Josh Bryan <> wrote:
>>> Hi,
>>> I am looking into CouchDB as a solution to store a bunch (approx 70
>>> million) archived documents.  While planning for the import process, I
>>> did some benchmarking to figure out how long the import will take.  I
>>> get about 50-70 inserts per second on average.  However, when I looked
>>> for the bottleneck, I couldn't figure it out.  I am connected to the
>>> database via a fast lan and can verify that the network is not
>>> saturated.  I can also verify that disk IO is not saturated.  The only
>>> clue is that of the 4 cpus on the server, it seems that only one is
>>> getting fully loaded.  Also, of the 5 erlang processes I can see
>>> running, only one of them seems to be getting most of the cpu time.  I
>>> know that erlang is built with smp enabled, so if it is cpu bound, why
>>> can't it make use of the other 3 processors?
>>> I thought that perhaps there was some internal write lock issue per
>>> database that allowed only one thread to write to a db at a time, so I
>>> tried running the benchmarks while hitting multiple databases, but still
>>> got the same write rate across the databases.  Is there some globally
>>> shared resource in couchdb that limits all writes to a single thread?
>>> Thanks,
>>> Josh
>> Before we can help you diagnose the performance you're seeing, could
>> you tell us the version of CouchDB and the version of Erlang that you
>> are using? It wouldn't hurt to describe the hardware in more detail
>> either.
> I am seeing similar results on two systems.
> System 1:
> Quad core Intel(R) Xeon(R) CPU 5160  @ 3.00GHz
> 2 GB ram
> Linux 2.6.18-4  -- Debian Lenny
> Erlang (BEAM) emulator version 5.6.3 [source] [64-bit] [smp:4]
> [async-threads:0] [kernel-poll:false]
> couchdb - Apache CouchDB 0.8.0-incubating
> System 2:
> Intel(R) Pentium(R) D CPU 3.00GHz
> 3 GB ram
> Erlang (BEAM) emulator version 5.5.5 [source] [async-threads:0]
> [kernel-poll:false]
> couchdb - Apache CouchDB 0.9.0a724455-incubating
> Thanks

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