Migrated from 8.3 to 9.0 - need to update config (re-post)

Hello performance wizards! (Sorry for the re-post if this appears twice - I see no evidence e-mailing to pgsql-perfomrance is working yet.)

My client has migrated his 8.3 hosted DB to new machines
running PG 9.0. It’s time to look at the config settings.

Immediately below are the config settings.

The specifics of the DB and how it is used is below
that, but in general let me say that this is a full-time ETL system, with only a
handful of actual “users” and automated processes over 300 connections running
“import” programs 24/7.

I appreciate the help,

Carlo

The host system:

Intel® Xeon® Processor X5560 (8M Cache, 2.80 GHz, 6.40
GT/s Intel® QPI) x 2, dual quad core
48 GB RAM
RAID 10, 6 X 600 GB 15krpm
SAS)
LINUX Redhat/Centos
2.6.18-164.el5

Sys admin says that battery-backup RAID controller and
consequent write settings should have no impact on performance. Is this
true?

Current config and my thoughts on what to do with it. If
it isn’t mentioned here, the values are default
values:

#
===========================================================

max_connections =
300
shared_buffers =
500MB # At 48GB of RAM, could we go to 2GB

# - what is the impact on LINX config?
effective_cache_size =
2457MB # Sys admin says assume 25% of 48GB

# is used by OS and other apps
work_mem =
512MB # Complex reads are called many times a second

# from each connection, so what should this be?
maintenance_work_mem =
256MB # Should this be bigger - 1GB at least?
checkpoint_segments =
128 # There is lots of write activity; this is high

# but could it be higher?

#checkpoint_completion_target
not set;
# Recommendation appears to
be .9 for our 128 checkpoint segments

default_statistics_target =
200 # Deprecated?

#autovacuum_freeze_max_age
not set;
# recommendation is
1,000,000 for non-activity.

# What is the metric for
wal_buffers setting?
wal_buffers =
4MB # Looks low, recommendation appears to be 16MB.

# Is it really "set it and forget it"?

#synchronous_commit not set;

# Recommendation is to turn
this off and leave fsync on

#fsync not set;

# Recommendation is to
leave this on

#wal_level not set;

# Do we only needed for
replication?

#max_wal_senders not set;

# Do we only needed for
replication?

# The issue of
vacuum/analyze is a tricky one.
# Data imports are running
24/7. One the DB is seeded, the vast majority
# of write activity is
updates, and not to indexed columns.
# Deletions are vary
rare.
vacuum_cost_delay =
20ms

# The background writer has
not been addressed at all.
# Can our particular setup
benefit from changing
# the bgwriter
values?
bgwriter_lru_maxpages =
100 # This is the default;

listen_addresses =
'*'
port =
5432
log_destination =
'stderr'
logging_collector =
on
log_directory =
'pg_log'
log_filename =
'postgresql-%a.log'
log_truncate_on_rotation =
on
log_rotation_age =
1d
log_rotation_size =
0
log_line_prefix =
'%t'
track_counts =
on
#
===========================================================

The DB is pretty large, and organized by schema. The
most active are:

1)
One “Core” schema
a.
100 tables
b.
Typical row counts in the low
millions.
c.
This represents the enterprise’s core data.

d.
Equal read/write activity
2)
Multiple “Import” schemas
a.
Contain several thousand raw “flat file”
tables
b.
Ragged column structure, up to hundreds of
columns
c.
Erratic row counts, from dozens of rows to 1
million
d.
Each table sequentially read once, only
status fields are written back
3)
One “Audit” schema
a.
A new log table is created every
month
b.
Typical row count is 200
million
c.
Log every write to the “Core”
d.
Almost entirely write operations, but the few
read operations that are done have to be fast owing to the size of the
tables
e.
Links the “Core” data to the “Import”
data

There are next to no “users” on the system – each
connection services a constantly running import process which takes the incoming
“import” data, analyzes the “core” data and decides how to distil the import
into the core.

Analytical Processes are not
report-oriented
The “Core” reads are mostly single row
results
The “Import” reads are 1,000 row
pages
There is next to no use of aggregate
queries

Transactional Processes are a steady stream of
writes
Not bursty or sporadic
Overwhelmingly inserts and updates, next to no
deletes
Each transaction represents 10 – 50 writes to the “core”
schema