Re: postgresql-8.0.1 performance tuning

Martin Fandel wrote:

> Hi @ all,
>
> i'm trying to tune my postgresql-db but i don't know if the values are
> right
> set.
>
> I use the following environment for the postgres-db:
>
> ######### Hardware ############
> cpu: 2x P4 3Ghz
> ram: 1024MB DDR 266Mhz
>
> partitions:
> /dev/sda3 23G 9,6G 13G 44% /
> /dev/sda1 11G 156M 9,9G 2% /var
> /dev/sdb1 69G 13G 57G 19% /var/lib/pgsql
>
> /dev/sda is in raid 1 (2x 35GB / 10000upm / sca)
> /dev/sdb is in raid 10 (4x 35GB / 10000upm / sca)
> ######### /Hardware ############

You probably want to put the pg_xlog file onto /dev/sda rather than
having it in /dev/sdb. Having it separate from the data usually boosts
performance a lot. I believe you can just mv it to a different
directory, and then recreate it as a symlink. (Stop the database first :)

>
> ######### Config ############
> /etc/sysctl.conf:
> kernel.shmall = 786432000
> kernel.shmmax = 786432000
>
Not really sure about these two.

> /etc/fstab:
> /dev/sdb1 /var/lib/pgsql reiserfs
> acl,user_xattr,noatime,data=writeback 1 2
>
Seems decent.

> /var/lib/pgsql/data/postgresql.conf
> superuser_reserved_connections = 2
> shared_buffers = 3000
> work_mem = 131072
> maintenance_work_mem = 131072

These both seem pretty large. But it depends on how many concurrent
connections doing sorting/hashing/etc you expect. If you are only
expecting 1 connection, these are probably fine. Otherwise with 1GB of
RAM I would probably make work_mem more like 4096/8192.
Remember, running out of work_mem means postgres will spill to disk,
slowing that query. Running out of RAM causes the system to swap, making
everything slow.

> max_stack_depth = 2048
> max_fsm_pages = 20000
> max_fsm_relations = 1000
> max_files_per_process = 1000
> vacuum_cost_delay = 10
> vacuum_cost_page_hit = 1
> vacuum_cost_page_miss = 10
> vacuum_cost_page_dirty = 20
> vacuum_cost_limit = 200
> bgwriter_delay = 200
> bgwriter_percent = 1
> bgwriter_maxpages = 100
> fsync = true
> wal_sync_method = fsync
> wal_buffers = 64
> commit_delay = 0
> commit_siblings = 5
> checkpoint_segments = 256
> checkpoint_timeout = 900
> checkpoint_warning = 30
> effective_cache_size = 10000
> random_page_cost = 4
> cpu_tuple_cost = 0.01
> cpu_index_tuple_cost = 0.001
> cpu_operator_cost = 0.0025
> geqo = true
> geqo_threshold = 12
> geqo_effort = 5
> geqo_pool_size = 0
> geqo_generations = 0
> geqo_selection_bias = 2.0
> deadlock_timeout = 1000
> max_locks_per_transaction = 64
> ######### /Config ############
>
> ######### Transactions ############
> we have about 115-300 transactions/min in about 65 tables.
> ######### /Transactions ############
>
> I'm really new at using postgres. So i need some experience to set this
> parameters in the postgresql- and the system-config. I can't find standard
> calculations for this. :/ The postgresql-documentation doesn't help me to
> set the best values for this.
>
> The database must be high-availble. I configured rsync to sync the
> complete
> /var/lib/pgsql-directory to my hot-standby. On the hotstandby i will
> make the
> dumps of the database to improve the performance of the master-db.
>
I didn't think an rsync was completely valid. Probably you should look
more into Slony.
http://slony.info

It is a single-master asynchronous replication system. I believe it is
pretty easy to setup, and does what you really want.

> In my tests the synchronization works fine. I synchronised the hole
> directory
> and restarted the database of the hotstandby. While restarting,
> postgresql turned
> back the old (not archived) wals and the database of my hotstandby was
> consistent. Is this solution recommended? Or must i use archived wal's
> with
> real system-snapshots?
>
> best regards,
>
> Martin Fandel

John
=:->