Re: Bumping block size to 16K on FreeBSD...

> > > Early performance tests on my laptop suggest it's about 8%
> > > faster for writing when both the FS and PostgreSQL use 16K
> > > blocks.
> >
> > BTW, I don't really believe that one set of tests, conducted on
> > one single machine, are anywhere near enough justification for
> > changing this value.  Especially not if it's a laptop rather than
> > a typical server configuration.  You've got considerably less I/O
> > bandwidth in proportion to CPU horsepower than a server.  Why is
> > that an issue?  Well, a larger block size will substantially
> > increase our WAL overhead (because we tend to dump whole blocks
> > into WAL at the slightest provocation) and on slower machines the
> > CRC64 calculations involved in WAL entries are a significant cost.
> > On a machine with less CPU and more disk horsepower than you
> > tested, the tradeoffs could be a lot different.
>
> Sean, can we get a copy of your test set?  And any scripts that you
> have for running the tests?

Unfortunately not, my tests were simply re-initdb'ing and loading in
my schema.  I have some read tests I'm going to perform here in a bit,
but I'm waiting for kde to finish compiling before I start testing.
I have another tests machine that I'm going to task with comparing 16K
and 8K blocks.  It's not SCSI, but I don't have any available machines
that I can newfs + reinstall PostgreSQL on.  I was thinking about
running the regression tests 10x ...

-sc

-- 
Sean Chittenden