We use PostgreSQL 7.x on both OS X and Linux. We used to run OS X in
production, but due to numerous problems we switched to Linux. OS X
was not stable at all, especially under load. It was also a poor
performer under load or not.

In my tests, a P3/800, 512MB RAM (100MHz bus) was consistently faster
at all queries than a G4/1.25GHz, 1.5GB RAM (266MHz bus) for our
application. Both machines had single IDE drives.

Another thing to consider is that you can only get ATA drives with
Apple hardware. SCSI is not available from Apple, and SCSI devices
have very poor support under OS X. If a server with ATA drives goes
down at the wrong time, you can lose data. This happened to us with
our production OS X server last year. An extended power outage ran
out the UPS battery, the shutdown script did not stop the server in
time, and we had to restore from an earlier backup. For details on
why this can happen with ATA drives, see this thread:

<http://archives.postgresql.org/pgsql-general/2003-10/msg01343.php>

Overall, PostgreSQL has been rock solid, very fast, and headache-free
on Linux. A complete change from OS X. Our main production
PostgreSQL server has been up for 234 days now. In that period, the
only downtime for PostgreSQL has been for planned upgrades.

As a side note, we've also had major problems running multi-threaded
servers on OS X which run great (stable and much, much faster) on
Linux.

- Jeff




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VisionLink, Inc.
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We were using OS X 10.2 in production. We currently use 10.3 for our
development machines.

I would be shocked if a processor could fix stability issues in an
operating system. As for performance, I cannot say how much better
PostgreSQL runs on a G5 as we don't have any G5s. In terms of
hardware specs, a G4/1.25Ghz should blow away a P3/800. But it
didn't for us, and I think that is because Linux/x86 is much more
efficient than OS X/ppc. I do not expect that to change with a newer
ppc processor.

Since your your developers believe a dual G5 to be plenty, you will
probably get more than enough performance from an XServe G5 and any
comparable 2-way Intel or AMD x86 system. PostgreSQL should handily
outperform 4D. If those systems are in your price range, and
stability isn't a big concern, you should probably go with the OS you
are more familiar with.

- Jeff


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Jeff Bohmer
VisionLink, Inc.
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On Nov 3, 2004, at 1:33 PM, Jeff Bohmer wrote:
Did you (or anyone) ever compare performance of PostgreSQL under PPC
Linux running on the G4 or G5?

-Kevin Murphy


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OS 10.3 IMHO is more stable then 10.2. I haven't us OS X in a
production environment only for development. I have yet to have any
problems with it crashing.

I haven't really run any tests to load it down but that's only because
I never expect to use in production. We have far too many IBM Servers
with battery backed up RAID controllers that I do not see a sudden
switch to any other platform.

If I was a gambling man I would put my money on Linux doing a better
job with postgres, but that's mainly because of the better hardware
options in regard to disks. If your DB is processor heavy the G5 will
most likely out perform x86 processors. If you go with the XRaid I
think all bets are off with regards to dollar for dollar PC/Mac
comparison..


On Wed, 03 Nov 2004 15:04:03 -0600, Jim Strickland
<jims (AT) americanroamer (DOT) com> wrote:
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on 11/3/04, Jeff Bohmer <bohmer (AT) visionlink (DOT) org> wrote:

In my experience, a G4/1.25GHz computer with standard apple drive was much
faster than the PC (Pentium 2+GHz, don't remember details) we tested running
Linux. Both machines had plenty of RAM, same PostgreSQL settings, etc. The PC
was much slower than the mac running backup/restore (more than 2x slower). The
queries we tested were slower as well. Both machines had IDE drives. I'd think
the Linux box could probably be made to be faster, but it had a long way togo
to even match the G4.

We have had excellent stability on both G4 and G5, MacOS 10.2.x and 10.3.x,
PostgreSQL 7.3.x and 7.4.x. The only time we experienced instability was just
after the G5 was released, the combination of G5, MacOS 10.2.7 and PostgreSQL
7.3.x just didn't work very well. Upgrading the G5 to MacOS 10.3.x and
PostgreSQL 7.4.x brought back the stability we expected and we haven't really
had any problems since.


Any specific examples? Apache 2.x with PHP 4.3.x has been running well on
various single and dual-cpu MacOS X boxes here.

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Deep Sky Technologies, Inc.

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One possible explanation for your results would be that the Mac IDE
drive lies about write completion while the PC IDE drive does not.
You mention a backup/restore test, which is very write-intensive.
Any system with an IDE drive that lies about write completion is
going to blow away (write performance-wise) a system with an IDE
drive that does not lie about it. Our tests last year were all with
SELECT queries to prevent this factor from skewing our results. (Our
app is read-heavy and we knew we would be getting a good hardware
RAID setup that could handle the writes.)

I do not have the same Apple hardware from a year ago to reproduce my
tests. If I get time in the next week, I can try something on the
same PC (RedHat 9, P3/800) vs. a G4/933, OS X Server 10.2.


Our primary OS X 10.2 server crashed very frequently. Sometimes more
than once per day. We changed machines and the crashes continued.
Apple HW test on both boxes showed no problems. The vast majority of
these crashes were under moderate load (~120 queries/min). A few
times, reindexing would cause a crash without any other DB activity.
With almost all of these crashes, there were no CrashReporter log
entries. At that point, we felt like we had no recourse but to try
something different (Linux/x86) and haven't looked back.

- Jeff

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Jeff Bohmer
VisionLink, Inc.
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old, and...not as stable as one could hope, especially if used for
other services.
OS X Server 10.3 is better / much more stable (the "good enough"
depends on what you are doing with it).

Still, I would recommend using the standard OS X 10.3 on a separate box
and tune the kernel params for optimal Postgres use, this is if you
already have one spare Mac for that. Upgrading to the G5 will only be
really usefull if you have very CPU intensive queries. If you are
essentially i/o bound, than faster disks make more sense, and as
previously said, fast disks on a Mac require a third-party SCSI card
and an external RAID or an xRaid. Can be expensive or "cheap"
depending on the disk amount you need.

I would make some benchmarks...
hth,
Philippe


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My guess is that you will get better performance from a similarly priced
Dual Opteron for the following reasons:

1) OS-X is not 64-bit yet, 64-bit Linux/BSD OS's are available
2) GCC is far better tuned for x86 than PowerPC/Itanium/etc
3) Postgres *seems* to prefer Opteron's ondie memory controller
architecture over shared bus -- especially in SMP configs

Is it enough of a difference? If you needed to eek out every possible %
performance because you have a critical production need, then the answer
is yes. Otherwise, it's easier to stick with the OS you know.


Jim Strickland wrote:

I've been working with PostgreSQL on OS X (G4, G5 and dual G5 systems)
for a few months now, and overall I've been really pleased; for us, it
seems to be a good match.

If you have both an OS X and a Linux or BSD system available, you could
run pgbench against both and get a rough idea on how they compare.


On Nov 4, 2004, at 1:33 PM, William Yu wrote:


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