Configuracion de postgresql Sobre cargado - Mailing list pgsql-admin

He estado leyendo sobre la configuracion de postgresql, pero tengo un
servidor que no me da el rendimiento que deveria de dar, lo monitoreo con
top, ps y pg_stat_activity y para lo que esta haciendo no deberia de ponerse
tan lento a como se pone, las tablas estan bien indexadas y se realizan
vacuum regularmente.

Las caracteristicas del servidor son:

4 Procesadores Intel Xeon Duales de 3.0Ghz
12 GB de Memoria RAM
El sistema esta operativo esta en 2 discos  en RAID 1
La base de datos esta en 4 discos en RAID 5
Es un servidor dell (No recuerdo el modelo lo administro remotamente)
S.O Slackware 11.0 Linux 2.6.17.7

A alcanzado 2000 conexiones simultaneas al postgresql  en max_connections le
puse  3000 para que sobrara un poco para procesos nuevos.
Tube que dividir la carga con otro servidor para que trabajara mejor y si
pues a fuerza mejoro pero por que se ahora solo alcanza a tener 500
conexiones simultaneas, pero aun asi lo sigo viendo con mucha carga.

Mi duda es mas que nada sobre la configuracion de memoria que deberia de
tener en shared_buffers y effective_cache_size.

Su ayuda se los agradeceria mucho.

En alguna pagina de internet encontre esto:

Tuning PostgreSQL for performance
2 Some basic parameters
2.1 Shared buffers

#  Start at 4MB (512) for a workstation
# Medium size data set and 256-512MB available RAM: 16-32MB (2048-4096)
# Large dataset and lots of available RAM (1-4GB): 64-256MB (8192-32768)

Entonces si yo tengo 12GB de RAM es correcto que use en shared_buffers =
98304??
tambien he leido que aumentar mucho la shared_buffers alenta los procesos,
le puse 81920 se hacerca a lo correcto?? (lo multiplique por 10)

Estas son algunas seciones de configuracion del archivo postgresql.conf

#---------------------------------------------------------------------------
# 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
#hba_file = 'ConfigDir/pg_hba.conf'    # host-based authentication file
#ident_file = 'ConfigDir/pg_ident.conf'    # IDENT configuration file

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


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

# - Connection Settings -

listen_addresses = '*'        # what IP address(es) to listen on;
                    # comma-separated list of addresses;
                    # defaults to 'localhost', '*' = all
port = 5432
max_connections = 3000
# 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 = 2
#unix_socket_directory = ''
#unix_socket_group = ''
#unix_socket_permissions = 0777        # octal
#bonjour_name = ''            # defaults to the computer name



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

# - Memory -


shared_buffers = 81920            # min 16 or max_connections*2, 8KB each
temp_buffers = 5000            # min 100, 8KB each
max_prepared_transactions = 1000    # can be 0 or more
# note: increasing max_prepared_transactions costs ~600 bytes of shared
memory
# per transaction slot, plus lock space (see max_locks_per_transaction).
work_mem = 10240            # min 64, size in KB
maintenance_work_mem = 253952        # min 1024, size in KB
max_stack_depth = 4096            # min 100, size in KB

# - Free Space Map -

#max_fsm_pages = 20000            # min max_fsm_relations*16, 6 bytes each
#max_fsm_relations = 1000        # min 100, ~70 bytes each

# - Kernel Resource Usage -

#max_files_per_process = 1000        # min 25
#preload_libraries = ''

# - 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 = 200            # 10-10000 milliseconds 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 = on                # turns forced synchronization on or off
#wal_sync_method = fsync        # the default is the first option
                    # supported by the operating system:
                    #   open_datasync
                    #   fdatasync
                    #   fsync
                    #   fsync_writethrough
                    #   open_sync
#full_page_writes = on            # recover from partial page writes
#wal_buffers = 8            # min 4, 8KB each
#commit_delay = 0            # range 0-100000, in microseconds
#commit_siblings = 5            # range 1-1000

# - Checkpoints -

checkpoint_segments = 20        # in logfile segments, min 1, 16MB each
#checkpoint_timeout = 300        # range 30-3600, in seconds
#checkpoint_warning = 30        # in seconds, 0 is off

# - Archiving -

#archive_command = ''            # command to use to archive a logfile
                    # segment


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

# - Planner Method Configuration -

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

# - Planner Cost Constants -

effective_cache_size = 65536        # typically 8KB each
#random_page_cost = 4            # units are one sequential page fetch
                    # cost
#cpu_tuple_cost = 0.01            # (same)
#cpu_index_tuple_cost = 0.001        # (same)
#cpu_operator_cost = 0.0025        # (same)


El sysctl.conf

contiene lo siguiente:
kernel.shmmax = 970170573
kernel.shmall = 970170573
kernel.sem = 400 42000 32 1024
vm.overcommit_memory = 2

Es correcta la configuracion que tengo?
Alguna sugerencia?

Gracias de antemano....

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