Re: Rather large LA - Mailing list pgsql-performance

Hi Andy,

It's not a new issue no, It's a legacy system that is in no way ideal but is also not in a position to be overhauled.
Indexesare correct, tables are up to 25 million rows.     

On startup, it hits CPU more than IO, I'll provide some additional stats after I restart it tonight.

Server logs have been reviewed and where possible, slow queries have been fixed.

Autovacuum has been disabled and set to run manually via cron during a quiet period and fsync has recently been turned
offto gauge any real world performance increase, there is battery backup on the raid card providing some level of
resilience.

Thanks

Richard


On 5 Sep 2011, at 14:39, Andy Colson wrote:

> On 09/05/2011 05:28 AM, Richard Shaw wrote:
>>
>> Hi,
>>
>> I have a database server that's part of a web stack and is experiencing prolonged load average spikes of up to 400+
whenthe db is restarted and first accessed by the other parts of the stack and has generally poor performance on even
simpleselect queries. 
>>
>
> Is the slowness new?  Or has it always been a bit slow?  Have you checked for bloat on your tables/indexes?
>
> When you start up, does it peg a cpu or sit around doing IO?
>
> Have you reviewed the server logs?
>
>
> autovacuum                     | off
>
> Why?  I assume that's a problem.
>
> fsync                          | off
>
> Seriously?
>
>
> -Andy
>
>
>
>> There are 30 DBs in total on the server coming in at 226GB.  The one that's used the most is 67GB and there are
another29 that come to 159GB. 
>>
>> I'd really appreciate it if you could review my configurations below and make any suggestions that might help
alleviatethe performance issues.  I've been looking more into the shared buffers to the point of installing the contrib
moduleto check what they're doing, possibly installing more RAM as the most used db @ 67GB might appreciate it, or
movingthe most used DB onto another set of disks, possible SSD. 
>>
>>
>> PostgreSQL 9.0.4
>> Pgbouncer 1.4.1
>>
>> Linux 2.6.18-238.9.1.el5 #1 SMP Tue Apr 12 18:10:13 EDT 2011 x86_64 x86_64 x86_64 GNU/Linux
>>
>> CentOS release 5.6 (Final)
>>
>> 4 x Intel Xeon-NehalemEX E7540-HexCore [2GHz] ( 24 physical cores )
>> 32GB DDR3 RAM
>> 1 x Adaptec 5805 Z  SATA/SAS RAID with battery backup
>> 4 x Seagate Cheetah ST3300657SS 300GB 15RPM SAS drives in RAID 10
>> 1 x 500GB 7200RPM SATA disk
>>
>> Postgres and the OS reside on the same ex3 filesystem, whilst query and archive logging go onto the SATA disk which
isalso ext3. 
>>
>>
>>               name              |                                                  current_setting
>>
--------------------------------+-------------------------------------------------------------------------------------------------------------------
>>  version                        | PostgreSQL 9.0.4 on x86_64-unknown-linux-gnu, compiled by GCC gcc (GCC) 4.1.2
20080704(Red Hat 4.1.2-48), 64-bit 
>>  archive_command                | tar jcf /disk1/db-wal/%f.tar.bz2 %p
>>  archive_mode                   | on
>>  autovacuum                     | off
>>  checkpoint_completion_target   | 0.9
>>  checkpoint_segments            | 10
>>  client_min_messages            | notice
>>  effective_cache_size           | 17192MB
>>  external_pid_file              | /var/run/postgresql/9-main.pid
>>  fsync                          | off
>>  full_page_writes               | on
>>  lc_collate                     | en_US.UTF-8
>>  lc_ctype                       | en_US.UTF-8
>>  listen_addresses               |
>>  log_checkpoints                | on
>>  log_destination                | stderr
>>  log_directory                  | /disk1/pg_log
>>  log_error_verbosity            | verbose
>>  log_filename                   | postgresql-%Y-%m-%d_%H%M%S.log
>>  log_line_prefix                | %m %u %h
>>  log_min_duration_statement     | 250ms
>>  log_min_error_statement        | error
>>  log_min_messages               | notice
>>  log_rotation_age               | 1d
>>  logging_collector              | on
>>  maintenance_work_mem           | 32MB
>>  max_connections                | 1000
>>  max_prepared_transactions      | 25
>>  max_stack_depth                | 4MB
>>  port                           | 6432
>>  server_encoding                | UTF8
>>  shared_buffers                 | 8GB
>>  superuser_reserved_connections | 3
>>  synchronous_commit             | on
>>  temp_buffers                   | 5120
>>  TimeZone                       | UTC
>>  unix_socket_directory          | /var/run/postgresql
>>  wal_buffers                    | 10MB
>>  wal_level                      | archive
>>  wal_sync_method                | fsync
>>  work_mem                       | 16MB
>>
>>
>> Pgbouncer config
>>
>> [databases]
>> * = port=6432
>> [pgbouncer]
>> user=postgres
>> pidfile = /tmp/pgbouncer.pid
>> listen_addr =
>> listen_port = 5432
>> unix_socket_dir = /var/run/postgresql
>> auth_type = trust
>> auth_file = /etc/pgbouncer/userlist.txt
>> admin_users = postgres
>> stats_users = postgres
>> pool_mode = session
>> server_reset_query = DISCARD ALL;
>> server_check_query = select 1
>> server_check_delay = 10
>> server_idle_timeout = 5
>> server_lifetime = 0
>> max_client_conn = 4096
>> default_pool_size = 100
>> log_connections = 1
>> log_disconnections = 1
>> log_pooler_errors = 1
>> client_idle_timeout = 30
>> reserve_pool_size = 800
>>
>>
>> Thanks in advance
>>
>> Richard
>>
>>
>