Re: Best COPY Performance

[Stefan Kaltenbrunner <stefan(at)kaltenbrunner(dot)cc>]

Luke Lonergan wrote:
> Stefan,
>
> On 10/30/06 8:57 AM, "Stefan Kaltenbrunner" <stefan(at)kaltenbrunner(dot)cc> wrote:
>
> > > We've found that there is an ultimate bottleneck at about 12-14MB/s despite
> > > having sequential write to disk speeds of 100s of MB/s.  I forget what the
> > > latest bottleneck was.
> > I have personally managed to load a bit less then 400k/s (5 int columns
> > no indexes) - on very fast disk hardware - at that point postgresql is
> > completely CPU bottlenecked (2,6Ghz Opteron).
>
> 400,000 rows/s x 4 bytes/column x 5 columns/row = 8MB/s
>
> > Using multiple processes to load the data will help to scale up to about
> >   900k/s (4 processes on 4 cores).

yes I did that about half a year ago as part of the CREATE INDEX on a 
1,8B row table thread on -hackers that resulted in some some the sorting 
improvements in 8.2.
I don't think there is much more possible in terms of import speed by 
using more cores (at least not when importing to the same table) - iirc 
I was at nearly 700k/s with two cores and 850k/s with 3 cores or such ...

> 18MB/s?  Have you done this?  I've not seen this much of an improvement
> before by using multiple COPY processes to the same table.
>
> Another question: how to measure MB/s - based on the input text file?  On
> the DBMS storage size?  We usually consider the input text file in the
> calculation of COPY rate.


yeah that is a good questions (and part of the reason why I cited the 
rows/sec number btw.)


Stefan