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Published on john.parnefjord.se (http://john.parnefjord.se)

PostgreSQL configuration

By johnp
Created 2008-04-10 11:21

We run PostgreSQL for some large databases and it works very good. The servers have 32GB RAM each and is connected to a fast SAN, so what should you expect. But there are some important things that need to be considered in order to maximize the performance.

So, in order to maximize performance the disks where data resides are using the XFS filesystem and mounted using noatime. To start with we used 300GB disks at 10000 rpms, using RAID 5. These were interal disks shipped with the server and could unfortunately not be smaller as the data wouldn't fit on smaller disks. But the disks were way to slow and we switched to a SAN-system with smaller and faster disks, 146 GB 15000 rpms. With the move to the SAN the RAID configuration was also changed to RAID 10 to gain performance, with the XLOG and PostgreSQL data put on separate disks. This had a major impact on performance, but there is of course a price tag comming with it.

The following values has been changed/added to /etc/sysctl.conf: 

kernel.shmmax=25769803776

# See to that no process overcommit memory
# http://www.enterprisedb.com/documentation/kernel-resources.html
vm.overcommit_memory=2

Check that the database is using integers as primary keys not chars. For the web interface we use pgpool to access the database.

Vacuuming is done as a weekly job as we have quite few transactions during the week and then one large batchload every friday. Not all tables are vacuumed weekly, instead the vacuumprocess handles specific tables each week. After four weeks all tables are supposed to have been vacuumed.

After tuning postgresql.conf the final result was: 

# $Id: postgresql.conf 4503 2007-10-25 09:27:52Z john.parnefjord $

# -----------------------------
# PostgreSQL configuration file
# -----------------------------
#
# This file consists of lines of the form:
#
#   name = value
#
# (The '=' is optional.)  White space may be used.  Comments are introduced
# with '#' anywhere on a line.  The complete list of option names and
# allowed values can be found in the PostgreSQL documentation.  The
# commented-out settings shown in this file represent the default values.
#
# Please note that re-commenting a setting is NOT sufficient to revert it
# to the default value, unless you restart the server.
#
# Any option can also be given as a command line switch to the server,
# e.g., 'postgres -c log_connections=on'.  Some options can be changed at
# run-time with the 'SET' SQL command.
#
# This file is read on server startup and when the server receives a
# SIGHUP.  If you edit the file on a running system, you have to SIGHUP the
# server for the changes to take effect, or use "pg_ctl reload". Some
# settings, which are marked below, require a server shutdown and restart
# to take effect.
#
# Memory units:  kB = kilobytes MB = megabytes GB = gigabytes
# Time units:    ms = milliseconds s = seconds min = minutes h = hours d = days


#---------------------------------------------------------------------------
# FILE LOCATIONS
#---------------------------------------------------------------------------

# The default values of these variables are driven from the -D command line
# switch or PGDATA environment variable, represented here as ConfigDir.

#data_directory = 'ConfigDir'		# use data in another directory
					# (change requires restart)
#hba_file = 'ConfigDir/pg_hba.conf'	# host-based authentication file
					# (change requires restart)
#ident_file = 'ConfigDir/pg_ident.conf'	# ident configuration file
					# (change requires restart)

# If external_pid_file is not explicitly set, no extra PID file is written.
#external_pid_file = '(none)'		# write an extra PID file
					# (change requires restart)


#---------------------------------------------------------------------------
# CONNECTIONS AND AUTHENTICATION
#---------------------------------------------------------------------------

# - Connection Settings -

listen_addresses = 'localhost,10.10.10.200' # what IP address(es) to listen on; 
					# comma-separated list of addresses;
					# defaults to 'localhost', '*' = all
					# (change requires restart)
#port = 5432				# (change requires restart)
max_connections = 150			# (change requires restart)
# Note: increasing max_connections costs ~400 bytes of shared memory per 
# connection slot, plus lock space (see max_locks_per_transaction).  You
# might also need to raise shared_buffers to support more connections.
#superuser_reserved_connections = 3	# (change requires restart)
#unix_socket_directory = ''		# (change requires restart)
#unix_socket_group = ''			# (change requires restart)
#unix_socket_permissions = 0777		# octal
					# (change requires restart)
#bonjour_name = ''			# defaults to the computer name
					# (change requires restart)

# - Security & Authentication -

#authentication_timeout = 1min		# 1s-600s
ssl = on					# (change requires restart)
#password_encryption = on
#db_user_namespace = off

# Kerberos
#krb_server_keyfile = ''			# (change requires restart)
#krb_srvname = 'postgres'		# (change requires restart)
#krb_server_hostname = ''		# empty string matches any keytab entry
					# (change requires restart)
#krb_caseins_users = off		# (change requires restart)

# - TCP Keepalives -
# see 'man 7 tcp' for details

#tcp_keepalives_idle = 0		# TCP_KEEPIDLE, in seconds;
					# 0 selects the system default
#tcp_keepalives_interval = 0		# TCP_KEEPINTVL, in seconds;
					# 0 selects the system default
#tcp_keepalives_count = 0		# TCP_KEEPCNT;
					# 0 selects the system default


#---------------------------------------------------------------------------
# RESOURCE USAGE (except WAL)
#---------------------------------------------------------------------------

# - Memory -

shared_buffers = 12GB			# min 128kB or max_connections*16kB
					# (change requires restart)
temp_buffers = 8MB			# min 800kB
max_prepared_transactions = 0		# can be 0 or more
					# (change requires restart)
# Note: increasing max_prepared_transactions costs ~600 bytes of shared memory
# per transaction slot, plus lock space (see max_locks_per_transaction).
work_mem = 64MB				# min 64kB
maintenance_work_mem = 512MB		# min 1MB
#max_stack_depth = 2MB			# min 100kB

# - Free Space Map -

max_fsm_pages = 10000000 # min max_fsm_relations*16, 6 bytes each
					# (change requires restart)
#max_fsm_relations = 1000		# min 100, ~70 bytes each
					# (change requires restart)

# - Kernel Resource Usage -

#max_files_per_process = 1000		# min 25
					# (change requires restart)
#shared_preload_libraries = ''		# (change requires restart)

# - Cost-Based Vacuum Delay -

#vacuum_cost_delay = 0			# 0-1000 milliseconds
#vacuum_cost_page_hit = 1		# 0-10000 credits
#vacuum_cost_page_miss = 10		# 0-10000 credits
#vacuum_cost_page_dirty = 20		# 0-10000 credits
#vacuum_cost_limit = 200		# 0-10000 credits

# - Background writer -

#bgwriter_delay = 200ms			# 10-10000ms between rounds
#bgwriter_lru_percent = 1.0		# 0-100% of LRU buffers scanned/round
#bgwriter_lru_maxpages = 5		# 0-1000 buffers max written/round
#bgwriter_all_percent = 0.333		# 0-100% of all buffers scanned/round
#bgwriter_all_maxpages = 5		# 0-1000 buffers max written/round


#---------------------------------------------------------------------------
# WRITE AHEAD LOG
#---------------------------------------------------------------------------

# - Settings -

fsync = off				# turns forced synchronization on or off
wal_sync_method = open_sync		# the default is the first option 
					# supported by the operating system:
					#   open_datasync
					#   fdatasync
					#   fsync
					#   fsync_writethrough
					#   open_sync
full_page_writes = off			# recover from partial page writes
wal_buffers = 256			# min 32kB
					# (change requires restart)
#commit_delay = 0			# range 0-100000, in microseconds
#commit_siblings = 5			# range 1-1000

# - Checkpoints -

checkpoint_segments = 256		# in logfile segments, min 1, 16MB each
checkpoint_timeout = 20min		# range 30s-1h
checkpoint_warning = 3min		# 0 is off

# - Archiving -

#archive_command = ''		# command to use to archive a logfile segment
#archive_timeout = 0		# force a logfile segment switch after this
				# many seconds; 0 is off


#---------------------------------------------------------------------------
# QUERY TUNING
#---------------------------------------------------------------------------

# - Planner Method Configuration -

#enable_bitmapscan = on
#enable_hashagg = on
#enable_hashjoin = on
#enable_indexscan = on
#enable_mergejoin = on
#enable_nestloop = on
#enable_seqscan = on
#enable_sort = on
#enable_tidscan = on

# - Planner Cost Constants -

#seq_page_cost = 1.0			# measured on an arbitrary scale
random_page_cost = 2.5			# same scale as above
#cpu_tuple_cost = 0.01			# same scale as above
#cpu_index_tuple_cost = 0.005		# same scale as above
#cpu_operator_cost = 0.0025		# same scale as above
effective_cache_size = 8GB

# - Genetic Query Optimizer -

#geqo = on
#geqo_threshold = 12
#geqo_effort = 5			# range 1-10
#geqo_pool_size = 0			# selects default based on effort
#geqo_generations = 0			# selects default based on effort
#geqo_selection_bias = 2.0		# range 1.5-2.0

# - Other Planner Options -

#default_statistics_target = 10		# range 1-1000
#constraint_exclusion = off
#from_collapse_limit = 8
#join_collapse_limit = 8		# 1 disables collapsing of explicit 
					# JOINs


#---------------------------------------------------------------------------
# ERROR REPORTING AND LOGGING
#---------------------------------------------------------------------------

# - Where to Log -

#log_destination = 'stderr'		# Valid values are combinations of 
					# stderr, syslog and eventlog, 
					# depending on platform.

# This is used when logging to stderr:
#redirect_stderr = off			# Enable capturing of stderr into log 
					# files
					# (change requires restart)

# These are only used if redirect_stderr is on:
#log_directory = 'pg_log'		# Directory where log files are written
					# Can be absolute or relative to PGDATA
#log_filename = 'postgresql-%Y-%m-%d_%H%M%S.log' # Log file name pattern.
					# Can include strftime() escapes
#log_truncate_on_rotation = off # If on, any existing log file of the same 
					# name as the new log file will be
					# truncated rather than appended to. But
					# such truncation only occurs on
					# time-driven rotation, not on restarts
					# or size-driven rotation. Default is
					# off, meaning append to existing files
					# in all cases.
#log_rotation_age = 1d			# Automatic rotation of logfiles will 
					# happen after that time.  0 to 
					# disable.
#log_rotation_size = 10MB		# Automatic rotation of logfiles will 
					# happen after that much log
					# output.  0 to disable.

# These are relevant when logging to syslog:
#syslog_facility = 'LOCAL0'
#syslog_ident = 'postgres'


# - When to Log -

#client_min_messages = notice		# Values, in order of decreasing detail:
					#   debug5
					#   debug4
					#   debug3
					#   debug2
					#   debug1
					#   log
					#   notice
					#   warning
					#   error

#log_min_messages = notice		# Values, in order of decreasing detail:
					#   debug5
					#   debug4
					#   debug3
					#   debug2
					#   debug1
					#   info
					#   notice
					#   warning
					#   error
					#   log
					#   fatal
					#   panic

#log_error_verbosity = default		# terse, default, or verbose messages

#log_min_error_statement = error	# Values in order of increasing severity:
				 	#   debug5
					#   debug4
					#   debug3
					#   debug2
					#   debug1
				 	#   info
					#   notice
					#   warning
					#   error
					#   fatal
					#   panic (effectively off)

#log_min_duration_statement = -1	# -1 is disabled, 0 logs all statements
					# and their durations.

#silent_mode = off			# DO NOT USE without syslog or 
					# redirect_stderr
					# (change requires restart)

# - What to Log -

#debug_print_parse = off
#debug_print_rewritten = off
#debug_print_plan = off
#debug_pretty_print = off
#log_connections = off
#log_disconnections = off
#log_duration = off
log_line_prefix = '%m %p %u '
#log_line_prefix = ''			# Special values:
					#   %u = user name
					#   %d = database name
					#   %r = remote host and port
					#   %h = remote host
					#   %p = PID
					#   %t = timestamp (no milliseconds)
					#   %m = timestamp with milliseconds
					#   %i = command tag
					#   %c = session id
					#   %l = session line number
					#   %s = session start timestamp
					#   %x = transaction id
					#   %q = stop here in non-session 
					#        processes
					#   %% = '%'
					# e.g. '<%u%%%d> '
#log_statement = 'none'			# none, ddl, mod, all
#log_hostname = off


#---------------------------------------------------------------------------
# RUNTIME STATISTICS
#---------------------------------------------------------------------------

# - Query/Index Statistics Collector -

#stats_command_string = on
#update_process_title = on

#stats_start_collector = on		# needed for block or row stats
					# (change requires restart)
#stats_block_level = off
stats_row_level = on
#stats_reset_on_server_start = off	# (change requires restart)


# - Statistics Monitoring -

#log_parser_stats = off
#log_planner_stats = off
#log_executor_stats = off
#log_statement_stats = off


#---------------------------------------------------------------------------
# AUTOVACUUM PARAMETERS
#---------------------------------------------------------------------------

autovacuum = off			# enable autovacuum subprocess?
					# 'on' requires stats_start_collector
					# and stats_row_level to also be on
#autovacuum_naptime = 1min		# time between autovacuum runs
#autovacuum_vacuum_threshold = 500	# min # of tuple updates before
					# vacuum
#autovacuum_analyze_threshold = 250	# min # of tuple updates before 
					# analyze
#autovacuum_vacuum_scale_factor = 0.2	# fraction of rel size before 
					# vacuum
#autovacuum_analyze_scale_factor = 0.1	# fraction of rel size before 
					# analyze
#autovacuum_freeze_max_age = 200000000	# maximum XID age before forced vacuum
					# (change requires restart)
#autovacuum_vacuum_cost_delay = -1	# default vacuum cost delay for 
					# autovacuum, -1 means use 
					# vacuum_cost_delay
#autovacuum_vacuum_cost_limit = -1	# default vacuum cost limit for 
					# autovacuum, -1 means use
					# vacuum_cost_limit


#---------------------------------------------------------------------------
# CLIENT CONNECTION DEFAULTS
#---------------------------------------------------------------------------

# - Statement Behavior -

#search_path = '"$user",public'		# schema names
search_path = '"$user",public'
#default_tablespace = ''		# a tablespace name, '' uses
					# the default
#check_function_bodies = on
#default_transaction_isolation = 'read committed'
#default_transaction_read_only = off
#statement_timeout = 0			# 0 is disabled
#vacuum_freeze_min_age = 100000000

# - Locale and Formatting -

datestyle = 'iso, ymd'
#timezone = unknown			# actually, defaults to TZ 
					# environment setting
#timezone_abbreviations = 'Default'     # select the set of available timezone
					# abbreviations. Currently, there are
					#   Default
					#   Australia
					#   India
					# However you can also create your own
					# file in share/timezonesets/.
#extra_float_digits = 0			# min -15, max 2
#client_encoding = sql_ascii		# actually, defaults to database
					# encoding

# These settings are initialized by initdb -- they might be changed
lc_messages = 'en_US.utf8'			# locale for system error message 
					# strings
lc_monetary = 'sv_SE.utf8'			# locale for monetary formatting
lc_numeric = 'sv_SE.utf8'			# locale for number formatting
lc_time = 'sv_SE.utf8'				# locale for time formatting

# - Other Defaults -

#explain_pretty_print = on
#dynamic_library_path = '$libdir'
#local_preload_libraries = ''


#---------------------------------------------------------------------------
# LOCK MANAGEMENT
#---------------------------------------------------------------------------

#deadlock_timeout = 1s
#max_locks_per_transaction = 64		# min 10
					# (change requires restart)
# Note: each lock table slot uses ~270 bytes of shared memory, and there are
# max_locks_per_transaction * (max_connections + max_prepared_transactions)
# lock table slots.


#---------------------------------------------------------------------------
# VERSION/PLATFORM COMPATIBILITY
#---------------------------------------------------------------------------

# - Previous Postgres Versions -

#add_missing_from = off
#array_nulls = on
#backslash_quote = safe_encoding	# on, off, or safe_encoding
default_with_oids = off
#escape_string_warning = on
#standard_conforming_strings = off
#regex_flavor = advanced		# advanced, extended, or basic
#sql_inheritance = on

# - Other Platforms & Clients -

#transform_null_equals = off


#---------------------------------------------------------------------------
# CUSTOMIZED OPTIONS
#---------------------------------------------------------------------------

#custom_variable_classes = ''		# list of custom variable class names
Source URL:
http://john.parnefjord.se/node/45