Hi,
I'm experiencing high WriteLatency levels in a Postgres server 9.3.20 hosted in Amazon RDS. So far it's been almost two months of investigation and people at AWS technical support don't seem to find the cause. I think it could be related to Postgres and the number of schema/tables in the database, that's why I post this issue here.
I have around 4600 schemas, each contains 62 tables. The DB size is only around 130 GB. the server has plenty of available RAM, CPU usage is less than 10% and there are only around 16 connections, but WriteLatency is unusually high.
As I don't have access to the server, I cannot see which are the process that are wiring to disk, but my guess is that each Postgres process is writing to disk for some reason.
This issue doesn't seem related to workload. If I restart the server, WriteLatency drops to normal levels and remains like that until, after some time (a few hours or a day), without any obvious reason, it spikes again and continues at high levels since then.
Is it possible that, for some reason, Postgres processes start writing to disk at some point due to reaching any internal limit? Maybe related to relcache/catcache/syscache? Any other thoughts?
Thanks
Juan
