Re: Performance advice

On Tue, 24 Jun 2003, Shridhar Daithankar wrote:

> On 24 Jun 2003 at 13:29, Shridhar Daithankar wrote:
> > > - I have at my disposal one other server which has 2 Xeons, 10,000 RPM SCSI
> > > drive. Would it make sense to put Postgres on it and leave my apps running
> > > on the more powerful 4 CPU server?
>
> Argh.. Forgot it first time.
>
> With java runnning on same machine, I would not trust that machine for having
> free RAM all the time, no matter how much RAM you have put into it.

There are always the -Xmx, -Xss, -Xms jvm switches,
to control stack (per thread) and heap sizes.

>
> Secondly you are running linux which is known to have weird behaviour problems
> when it runs low on memory.
>
> For both these reasons, I suggest you put your database on another machine. A
> dual CPU machine is more than enough. Put good deal RAM, around a GB and two
> SCSI disks, one for data and another for WAL. If you get RAID for data, great.
> But that should suffice otherwise as well.
>

I think the DB on another machine could be from something helpfull,
to an overkill, to a leg self shooting.
Depending on the type of the majority of queries and the network speed
someone should give an extra time to think about it.

> > >
> > > - Would a RAID setup make the disk faster? Because top rarely shows the
> > > CPUs above 50%, I suspect maybe the disk is the bottleneck.
> >
> > Yes it is. You need to move WAL to a different disk. Even if it is IDE. (OK
> > that was over exaggeration but you got the point). If your data directories and
> > WAL logs are on physically different disks, that should bump up performance
> > plenty.
>
> In addition to that, on linux, it matters a lot as in what filesystem you use.
> IMO ext3 is strict no-no. Go for either reiserfs or XFS.
>
> There is no agreement as in which file system is best on linux. so you need to
> experiment if you need every ounce of performance.
>
> And for that you got to try freeBSD. That would gave you plenty of idea about
> performance differences. ( Especially I love man hier and man tuning on
> freeBSD. Nothing on linux comes anywhere near to that)
>

Its like comparing Mazda with VVT-i.
Whould you expect to find the furniture fabric
specs in the main engine manual?

Besides all that, i must note that jdk1.4.1 runs pretty
nice on FreeBSD, and some efforts to run java
over the KSE libs have been done with success.

> Bye
> Shridhar
>
> --
> "Who is General Failure and why is he reading my hard disk ?"Microsoft spel
> chekar vor sail, worgs grate !!(By leitner(at)inf(dot)fu-berlin(dot)de, Felix von Leitner)
>
>
> ---------------------------(end of broadcast)---------------------------
> TIP 5: Have you checked our extensive FAQ?
>
> http://www.postgresql.org/docs/faqs/FAQ.html
>

--
==================================================================
Achilleus Mantzios
S/W Engineer
IT dept
Dynacom Tankers Mngmt
Nikis 4, Glyfada
Athens 16610
Greece
tel: +30-210-8981112
fax: +30-210-8981877
email: achill at matrix dot gatewaynet dot com
mantzios at softlab dot ece dot ntua dot gr