intel vs amd benchmark for pg server - Mailing list pgsql-general

Hi

I would like to upgrade my production pg server from a machine with
following specs
    celeron 900MHz, intel 810 motherboard, 512MB
    pc 133 sdram memory,
    PGDATA is on 2 ide 7200rpm drives under software raid 1,
    linux kernel 2.4.18

to a dual processor x86 machine.  Because I have read many
benchmarks about athlon handily beating pentium (e.g. one recent
review I saw had low end duron ~ 1GHz beating pentium 4
2.2GHz) I feel that an amd system will give me better
performance/price.  None of the benchmarks I saw/remember
was stressing a database server so I thought I would do a benchmark myself
to confirm indeed that athlon is the better choice.

To my great surprise I have to conclude that intel is the winner.

I am using pg version 7.2.1 for the test below.

The benchmark I am using is the time it takes to vacuum.  The production
server 900MHz celeron takes around 90 seconds.  Nightly backup dump
from the server makes a 3 GB file.

vacuum command is run on the production
server when server is experiencing least or small load.  fsync is off.
no vacuum memory is set i.e whatever the default is.

My workstation specs is amd 1.33GHz, 192MB SDRAM, SIS motherboard,
$PGDATA is on a single 5400rpm drive.  I have loaded the
dump file from the production server on this machine and
vacuum takes more than 2 minutes.  This surprised me and I remebered
doing a benchmark of kernel compilation when I acquired this box
last year.  At that time kernel compilation time scales "more or less" linearly
with cpu speed among all machines I have tested i.e faster processor means faster
compilation.  Since then I did make some changes to the box.  So I redo
kernel compilation test again on the machies below and
it still it scales "more or less" linearly with cpu speed

All tests below were done on systems other than production server
and minimal number of other processes are running.
postgresql.conf is not changed.

There are two numbers I get from the vacuum test.   First one t1
is the vacuum time immediately after the database is restored.
The other t2 is the time for subsequent vacuums.

$ initdb
$ pg_ctl -l log -o "-F"  start
$ psql template1 < dump
$ time vacuumdb -z what            #  <----- get first time t1
$ time vacuumdb -z what
.
.     repeat a number of times
.
.
.
$ time vacuumdb -z what            #  <------ get second time t2

------------

In all systems t1 > t2 but I will only report t2 below

system | motherboard|     cpu       |   memory          | PGDATA resides on           |   t2 (seconds)
------------------------------------------------------------------------------------------------------
1      | SIS        | ATHLON 1.33GHz | 192MB pc100 SDRAM | seagate 5400 udma 100 40GB  |   133

2      | INTEL      | celeron 566MHz | 64MB pc100 SDRAM  | maxtor 7200 udma 66 10 GB   |   87

2      | INTEL      | celeron 566MHz | 64MB pc100 SDRAM  | maxtor 5400 udma 66 20 GB   |   96

3      | ?hp laptop | duron 1GHZ     | 240MB SDRAM       | udma 100 20 GB unknown speed|   200
-----------

Notice that kernel compilation time scales "more or less" linearly with cpu speed on
all systems above except I did not do kernel compilation on system 2 on 5400rpm drive

The conclusion is that slower intel cpu vacuums quicker than faster amd cpu.

What do you all think?

k