Re: Upgrade to dual processor machine? - Mailing list pgsql-general

Hi Justin,

thanks for your answer, I will now try to deliver some more information
to you... but I am in particular a programmer, not a hacker ;-)) so please
excuse if I lack some knowledge in system things and stuff....

> - Have you run any system-performance tools apart from top, to figure
> out how the various parts of your system are operating?

nope. don't know any... which would you recommend for measurement of i/o
usage etc. ?

> The solution may turn out to be upgrading your disks instead
> of your CPU's (example only).

I will at least consider this... IDE disks are not that reliable either...

> Important question, how much memory can you get into that server?  Could
> you do 3GB or more?

no, sorry  -  1 GB is allready the upper limit... I consider migrating everything
to a new hardware, (dual?) intel xeon with perhaps even raid-v storage system with
a new upper limit of 12 GB RAM which will give me some upgrade-possibilies ... ;-))

> Something that would be *really nice* is if you have a second server
> with the same configuration hanging around that you can try stuff on.
> For example, loading it with a copy of all your data, changing the
> memory configuration, then testing it.

I actually DO have an identical second server, and the db is allready on it.
however, the system has a few problems concerning harddisk failuers and memory
problems (don't ever use it for running systems!! we had this server on the list
before... I almost gave up on this one, when suddenly all problems and crashes
were solved when moving to a different machine as suggested by tom lane ....)
... but for some testing purpose it sould be sufficient ;-))



> - Which version of the Linux kernel, and of RedHat?

redhat - linux kernel 2.4.7-10


> - If you do a ps (ps -ef) during a busy time, how many instances of the
> PostgreSQL process do you see in memory?  This will tell you how many
> ients have an open connection to the database at any time.

up to 40 clients are running... right now it's 21 processes and w shows
a load average of 1.92, 1.58, 1.59

> - How much data is in your database(s)?  Just to get an idea of your
> volume of data.

It's 3.6 GB at the moment in one database in 98 user tables.

> - If disk performance turns out to be the problem, would you consider
> moving to higher-end hard drives

allready considering ....


--

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Henrik Steffen
Geschäftsführer

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----- Original Message -----
From: "Justin Clift" <justin@postgresql.org>
To: "Henrik Steffen" <steffen@city-map.de>
Cc: <pgsql-general@postgresql.org>
Sent: Monday, November 11, 2002 8:44 AM
Subject: Re: [GENERAL] Upgrade to dual processor machine?


> Hi Henrik,
>
> Ok, you're machine is doing a decent amount of work, and will need
> looking at carefully.
>
> Going to get more specific about some stuff, as it'll definitely assist
> with giving you proper guidance here.
>
> - Have you run any system-performance tools apart from top, to figure
> out how the various parts of your system are operating?
>
> For example, by looking into and measuring the different parts of your
> system, you may find you have several processes simultaneously waiting
> to execute purely because the disk drives can't keep up with the
> requests.  The solution may turn out to be upgrading your disks instead
> of your CPU's (example only).  Without taking measurements to the point
> of understanding what's going on, you'll only be guessing.
>
> The most concerning aspect at the moment is this:
>
> "> - Have you configured the memory after installation of PostgreSQL, so
> > it's better optimised than the defaults?
> no - what should I do? Looking at 'top' right now, I see the following:
> Mem 1020808K av, 1015840K used, 4968K free, 1356K shrd, 32852K buff"
>
> This is telling me that the system is operating close to using all it's
> memory with running processes.  *Bad* for this kind of thing.  The
> default memory configuration for PostgreSQL is very lean and causes high
> CPU load and slow throughput.  You don't seem to have enough spare
> memory at the moment to really try adjusting this upwards.  :(
>
> Important question, how much memory can you get into that server?  Could
> you do 3GB or more?
>
> Something that would be *really nice* is if you have a second server
> with the same configuration hanging around that you can try stuff on.
> For example, loading it with a copy of all your data, changing the
> memory configuration, then testing it.
>
>
> Further system specific details needed:
>
> - Which version of the Linux kernel, and of RedHat?  Different version
> of the Linux kernel do things differently.  For example version 2.4.3
> does virtual memory differently than say version 2.4.17.
>
>
> - If you do a ps (ps -ef) during a busy time, how many instances of the
> PostgreSQL process do you see in memory?  This will tell you how many
> clients have an open connection to the database at any time.
>
>
> - How much data is in your database(s)?  Just to get an idea of your
> volume of data.
>
>
> - If disk performance turns out to be the problem, would you consider
> moving to higher-end hard drives?  This will probably mean an Ultra160
> or Ultra320 SCSI card, and drives to match.  That's not going to be
> totally cheap, but if you have a decent budget then it might be ok.
>
>
> As you can see, this could take a bit of time an effort to get right.
>
> Regards and best wishes,
>
> Justin Clift
>
>
> Henrik Steffen wrote:
> >
> > Hi Justin,
> >
> > here a little more information:
> >
> > > - Processor type and speed
> > Intel Pentium IV, 1.6 GHz
> >
> > > - Memory
> > 1024 MB ECC-RAM
> >
> > > - Disk configuration
> > 2 x 60 GB IDE (Raid 0)
> >
> > > - OS
> > Redhat Linux
> >
> > >
> > > - Do you do other stuff on it, apart from PostgreSQL?
> > No, it's a dedicated database server
> >
> > >
> > > - How many clients simultaneously connecting to it?
> > one webserver with max. 50 instances, approximately 10.000 users a day,
> > about 150.000 Pageviews daily. All pages are created on the fly using
> > mod_perl connecting to the db-server.
> >
> > > - What do the clients connect with?  JDBC/ODBC/libpq/etc?
> > I am using Pg.pm --- this is called libpq, isn't it?
> >
> > > - Have you configured the memory after installation of PostgreSQL, so
> > > it's better optimised than the defaults?
> > no - what should I do? Looking at 'top' right now, I see the following:
> > Mem 1020808K av, 1015840K used, 4968K free, 1356K shrd, 32852K buff
> >
> > So, what do you suggest to gain more performance?
> >
> > Thanks in advance,
>
> --
> "My grandfather once told me that there are two kinds of people: those
> who work and those who take the credit. He told me to try to be in the
> first group; there was less competition there."
>    - Indira Gandhi
>
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