Re: Inserting 8MB bytea: just 25% of disk perf used?

Matthew Wakeling:

> On Thu, 14 Jan 2010, fkater(at)googlemail(dot)com wrote:
> > Nevertheless: If your explanation covers all what can be
> > said about it then replacing the hard disk by a faster one
> > should increase the performance here (I'll try to check that
> > out).
>
> Probably. However, it is worth you running the test again, and looking at
> how busy the CPU on the machine is. The disc may be the bottleneck, or the
> CPU may be the bottleneck.

True.

I've changed the setting a bit:

(1) Replaced 7.200 disk by a 10.000 one, still sata though.

(2) Inserting rows only 10x times (instead of 100x times)
but 80mb each, so having the same amount of 800mb in total.

(3) Changed the WAL path to the system disk (by the
great 'junction' trick mentioned in the other posting), so
actually splitting the write access to the "system" disk and
the fast "data" disk.

And here is the frustrating result:

1. None of the 4 CPUs was ever more busy than 30% (never
less idle than 70%),

2. while both disks kept being far below the average write
performance: the "data" disk had 18 peaks of approx. 40 mb
but in total the average thoughput was 16-18 mb/s.

BTW:

* Disabling noatime and similar for ntfs did not change
things much (thanks though!).

* A short cross check copying 800mb random data file from
"system" to "data" disk showed a performance of constantly
75 mb/s.

So, I have no idea what remains as the bottleneck.

Felix