Re: Postgres configuration for 64 CPUs, 128 GB RAM... - Mailing list pgsql-performance

Marc Mamin wrote:
>
> Postgres configuration for 64 CPUs, 128 GB RAM...

there are probably not that much installation out there that large -
comments below

>
> Hello,
>
> We have the oppotunity to benchmark our application on a large server. I
> have to prepare the Postgres configuration and I'd appreciate some
> comments on it as I am not experienced with servers of such a scale.
> Moreover the configuration should be fail-proof as I won't be able to
> attend the tests.
>
> Our application (java + perl) and Postgres will run on the same server,
> whereas the application activity is low when Postgres has large
> transactions to process.
>
> There is a large gap between our current produtcion server (Linux, 4GB
> RAM, 4 cpus) and the benchmark server; one of the target of this
> benchmark is to verify the scalability of our application.
>

[...]
> Posgres version: 8.2.1

upgrade to 8.2.4

> File system:
>
> _http://en.wikipedia.org/wiki/ZFS_

way more important is what kind of disk-IO subsystem you have attached ...

>
>
>
> Planned configuration:
> --------------------------------
>
> # we don't expect more than 150 parallel connections,
> # but I suspect a leak in our application that let some idle connections
> open
>
> max_connections=2000
>
> ssl = off
>
> #maximum allowed
> shared_buffers= 262143

this is probably on the lower side for a 128GB box

>
> # on our current best production server with 4GB RAM (not dedicated to
> Postgres), work_mem is set to 600 MB
> # this limitation is probably the bottleneck for our application as the
> files in pgsql_tmp grows up to 15 GB
> # during large aggregations (we have a locking mechanismus to avoid
> parallel processing of such transactions)
> work_mem = 31457280  # (30 GB)

this is simply ridiculous - work_mem is PER SORT - so if your query
requires 8 sorts it will feel free to use 8x30GB and needs to be
multiplied by the number of concurrent connections.

>
> # index creation time is also an issue for us; the process is locking
> other large processes too.
> # our largest table so far is 13 GB + 11 GB indexes
> maintenance_work_mem = 31457280  # (30 GB)

this is ridiculous too - testing has shown that there is not much point
in going beyond 1GB or so

>
> # more than the max number of tables +indexes expected during the benchmark
> max_fsm_relations = 100000
>
> max_fsm_pages = 1800000

this is probably way to low for a database the size of yours - watch the
oputput of VACUUM VERBOSE on a database wide vacuum for some stats on that.

>
> # don't know if I schoud modify this.
> # seems to be sufficient on our production servers
> max_stack_depth = 2MB
>
> # vacuum will be done per hand between each test session
> autovacuum = off
>
>
>
> # required to analyse the benchmark
> log_min_duration_statement = 1000
>
>
> max_prepared_transaction = 100
>
>
> # seems to be required to drop schema/roles containing large number of
> objects
> max_locks_per_transaction = 128
>
>
>
>
> # I use the default for the bgwriter as I couldnt find recommendation on
> those
>
> #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
>
>
> #WAL
>
> fsync = on
>
> #use default
> #wal_sync_method
>
> # we are using 32 on our production system
> wal_buffers=64

values up to 512 or so have been reported to help on systems with very
high concurrency


what is missing here is your settings for:

effective_cache_size

and

random_page_cost



Stefan