RE: Expectations of MEM requirements for a DB with large tables.

Kuroi,

Thank you for the response.

I was not specifically thinking of diagnosing my crash, but if you are
curious...

 - about a 1000 error messgaes saying that kswapd could not do something
relating to allocating memory.

 - after stopping the "psql" job, it still took about 20 minutes before my
Linux OS recovered enough to reboot.

 - yep, used "psql", plan on using Perl-DBI soon... I guess from your
response I better make sure that whatever I use never does a full blown
'select *' on that table.

 - 2.2.17 from kernel.org, w/RAID patch.

 - PostgreSQL 7.0.2 was installed via the RPM from RedHat.

 - 98MB of RAM (this is a simple test system only)

 - 256MB of SWAP on a Linux SWAP Partition.

 - SWAP settings? Hmm... sorry this is where my novice level shows its
colors, didn't know I could modify it.

 - Other processes, sure tons of them...

Anyway, based upon your response, I understand that the 1 to 1 ratio is what
crashed my system.

Hmm, now you have me wondering though... I recall reading something that
mentioned that data storage size in PostgreSQL is about 6 times the size of
standard text, so, if my table size is about 5.5GB on the disk does this
mean I really could only need about well say... 5.5GB / 6 = 936MB of RAM?

Any idea?

-Michael Miyabara-McCaskey


> -----Original Message-----
> From: pgsql-general-owner@postgresql.org
> [mailto:pgsql-general-owner@postgresql.org]On Behalf Of KuroiNeko
> Sent: Sunday, November 05, 2000 9:54 PM
> To: pgsql-general@postgresql.org
> Subject: Re: [GENERAL] Expectations of MEM requirements for a DB with
> large tables.
>
>
>
>  Mike,
>
> > Anyway, I crashed  my system the other  day when I did a
> "select *" from
> > one
> > of my large tables (about 5.5gb in size).
>
>  Well.... It  takes abit more than  that to actually crash
> the system. Can
> you  give  more details?  What  _exactly_  happened?  Did it
> hang?  Kernel
> panicked? Something else.
>
> > Does anyone know what  the ratio of data output size  (say
> from a select)
> > to
> > the amount of
> > RAM used is?
>
>  It simply can't be  other than 1 : 1. Well, in a  sense. Did
> you use psql?
> Other app? If the  latter, what interface: API, DBI, other?
> Was it a local
> or remote request?
>
> > Other relevant info, RedHat Linux 2.2.17 kernel, PostgreSQL 7.0.2.
>
>  Is this a  genuine kernel, or the  one shipped by RH? Did
> you build PGSQL
> from sources or  was it a pre-built  binary? How much RAM do
> you have, how
> fast and big is your swap? Swap settings? Other processes running?
>  As you see, there  are more questions than answers at  this
> stage. Tell us
> more. Tuning the system has never been easy.
>