Effective IO Concurrency

[luis . roberto]

Hi! 

In PostgreSQL 13, the way of using effective_io_concurrency has changed. Until 
v12, I used 200 for this value (using SSD drives). Using the new formula 
described in [ https://www.postgresql.org/docs/13/release-13.html | 
https://www.postgresql.org/docs/13/release-13.html ] gives me 1176. However, in 
the documentation [ 
https://www.postgresql.org/docs/13/runtime-config-resource.html#GUC-EFFECTIVE-IO-CONCURRENCY
 | 
https://www.postgresql.org/docs/13/runtime-config-resource.html#GUC-EFFECTIVE-IO-CONCURRENCY
 ] it says that the maximum value allowed is 1000.