Re: Perf decreased although server is better

On Thu, Nov 3, 2016 at 9:51 AM, Benjamin Toueg <btoueg(at)gmail(dot)com> wrote:
>
> Stream gives substantially better results with the new server (before/after)

Yep, the new server can access RAM at about twice the speed of the old.

> I've run "bonnie++ -u postgres -d /tmp/ -s 4096M -r 1096" on both
> machines. I don't know how to read bonnie++ results (before/after)
> but it looks quite the same, sometimes better for the new,
> sometimes better for the old.

On most metrics the new machine looks better, but there are a few
things that look potentially problematic with the new machine: the
new machine uses about 1.57x the CPU time of the old per block
written sequentially ((41 / 143557) / (16 / 87991)); so if the box
becomes CPU starved, you might notice writes getting slower than on
the new box. Also, several of the latency numbers are worse -- in
some cases far worse. If I'm understanding that properly, it
suggests that while total throughput from a number of connections
may be better on the new machine, a single connection may not run
the same query as quickly. That probably makes the new machine
better for handling an OLTP workload from many concurrent clients,
but perhaps not as good at cranking out a single big report or
running dump/restore.

Yes, it is quite possible that the new machine could be faster at
some things and slower at others.

--
Kevin Grittner
EDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company