Re: PostgreSQL on Linux PC vs MacOS X

>> 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 to go
>> to even match the G4.
>
> 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.
I would say this test is not very meaningful as OS X Server 10.2 is
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

>
>
>> 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.
>
> 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
>
> --
>
> Jeff Bohmer
> VisionLink, Inc.
> _________________________________
> 303.402.0170 x121
> http://www.visionlink.org/
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