Thanks for the feedback guys.
The database will grow in size. This first client
years worth of data was 85mb (test to proof of
concept). The 05 datasets I expect to be much larger.
I think I may increase the work_mem and
maintenance_work_mem a bit more as suggested to.
I'm a bit still confused with max_connections.
I've been keeping the max_connections to the # of
Apache connections. Since, this is all currently one
one box and it's a web-based application. I wanted to
make sure it stuck with the same # of connections.
However, is there a formula or way to determine if a
current setup with memory etc to allow such
connections?
Exactly how is max_connections determined or is a
guess?
Again thanks for your help and Mr. Taylors.
Look forward to providing help when I got more a grasp
on things to !:)
-William
--- John A Meinel [EMAIL PROTECTED] wrote:
Puddle wrote:
Hello, I'm a Sun Solaris sys admin for a start-up
company. I've got the UNIX background, but now I'm
having to learn PostgreSQL to support it on our
servers :)
Server Background:
Solaris 10 x86
PostgreSQL 8.0.3
Dell PowerEdge 2650 w/4gb ram.
This is running JBoss/Apache as well (I KNOW the
bad
juju of running it all on one box, but it's all we
have currently for this project). I'm dedicating
1gb
for PostgreSQL alone.
So, far I LOVE it compared to MySQL it's solid.
The only things I'm kind of confused about (and
I've
been searching for answers on lot of good perf
docs,
but not too clear to me) are the following:
1.) shared_buffers I see lot of reference to making
this the size of available ram (for the DB).
However,
I also read to make it the size of pgdata
directory.
I notice when I load postgres each daemon is using
the
amount of shared memory (shared_buffers). Our
current
dataset (pgdata) is 85mb in size. So, I'm curious
should this size reflect the pgdata or the 'actual'
memory given?
I currently have this at 128mb
You generally want shared_buffers to be no more than
10% of available
ram. Postgres expects the OS to do it's own caching.
128M/4G = 3% seems
reasonable to me. I would certainly never set it to
100% of ram.
2.) effective_cache_size - from what I read this is
the 'total' allowed memory for postgresql to use
correct? So, if I am willing to allow 1GB of memory
should I make this 1GB?
This is the effective amount of caching between the
actual postgres
buffers, and the OS buffers. If you are dedicating
this machine to
postgres, I would set it to something like 3.5G. If
it is a mixed
machine, then you have to think about it.
This does not change how postgres uses RAM, it
changes how postgres
estimates whether an Index scan will be cheaper than
a Sequential scan,
based on the likelihood that the data you want will
already be cached in
Ram.
If you dataset is only 85MB, and you don't think it
will grow, you
really don't have to worry about this much. You have
a very small database.
3.) max_connections, been trying to figure 'how' to
determine this #. I've read this is
buffer_size+500k
per a connection.
ie. 128mb(buffer) + 500kb = 128.5mb per
connection?
Max connections is just how many concurrent
connections you want to
allow. If you can get away with lower, do so.
Mostly this is to prevent
connections * work_mem to get bigger than your real
working memory and
causing you to swap.
I was curious about 'sort_mem' I can't find
reference
of it in the 8.0.3 documentation, has it been
removed?
sort_mem changed to work_mem in 8.0, same thing with
vacuum_mem -
maintenance_work_mem.
work_mem and max_stack_depth set to 4096
maintenance_work_mem set to 64mb
Depends how much space you want to give per
connection. 4M is pretty
small for a machine with 4G of RAM, but if your DB
is only 85M it might
be plenty.
work_mem is how much memory a sort/hash/etc will use
before it spills to
disk. So look at your queries. If you tend to sort
most of your 85M db
in a single query, you might want to make it a
little bit more. But if
all of your queries are very selective, 4M could be
plenty.
I would make maintenance_work_mem more like 512M. It
is only used for
CREATE INDEX, VACUUM, etc. Things that are not
generally done by more
than one process at a time. And it's nice for them
to have plenty of
room to run fast.
Thanks for any help on this. I'm sure bombardment
of
newbies gets old :)
-William
Good luck,
John
=:-
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