I'm hosting my own Lemmy instance and trying to figure out how to optimize PSQL to reduce disk IO at the expense of memory.

I accept increased risk this introduces, but need to figure out parameters that will allow a server with a ton of RAM and reliable power to operate without constantly sitting with 20% iowait.

Current settings:
# DB Version: 15
# OS Type: linux
# DB Type: web
# Total Memory (RAM): 32 GB
# CPUs num: 8
# Data Storage: hdd

max_connections = 200
shared_buffers = 8GB
effective_cache_size = 24GB
maintenance_work_mem = 2GB
checkpoint_completion_target = 0.9
wal_buffers = 16MB
default_statistics_target = 100
random_page_cost = 4
effective_io_concurrency = 2
work_mem = 10485kB
min_wal_size = 1GB
max_wal_size = 4GB
max_worker_processes = 8
max_parallel_workers_per_gather = 4
max_parallel_workers = 8
max_parallel_maintenance_workers = 4
fsync = off
synchronous_commit = off
wal_writer_delay = 800
wal_buffers = 64MB
Most load comes from LCS script seeding content and not actual users.

Solution: My issue turned out to be really banal - Lemmy's PostgreSQL container was pointing at default location for config file (/var/lib/postgresql/data/postgresql.conf) and not at the location where I actually mounted custom config file for the server (/etc/postgresql.conf). Everything is working as expected after I updated docker-compose.yaml file to point PostgreSQL to correct config file. Thanks @bahmanm@lemmy.ml for pointing me in the right direction!

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[–] daq@lemmy.daqfx.com 1 points 1 year ago* (last edited 1 year ago)

I guess I could just use rsync to periodically sync RAM drive to disk or just rely on backups to restore running state in case of failure or just a restart. On a mostly idle server with few users this could probably work, but I don't think I'm quite ready for such a risky setup. Server is still perfectly usable at 15% iowait - i was just hoping I could reduce it with mechanisms built into PSQL. Appreciate the suggestion though.

Edit: I just want to say this would be an awesome feature for Docker/Podman to have an in-memory volume that syncs to disk either periodically or on container termination as an option.