Re: [EXTERNAL] Re: WIP: WAL prefetch (another approach)

On Wed, Aug 26, 2020 at 9:42 AM Sait Talha Nisanci
<Sait.Nisanci@microsoft.com> wrote:
> I have tried combination of SSD, HDD, full_page_writes = on/off and max_io_concurrency = 10/50, the recovery times
areas follows (in seconds):
 
>
>                                No prefetch          |     Default prefetch values  |          Default +
max_io_concurrency= 50
 
> SSD, full_page_writes = on      852             301                             197
> SSD, full_page_writes = off     1642            1359                            1391
> HDD, full_page_writes = on      6027            6345                            6390
> HDD, full_page_writes = off     738             275                             192

The regression on HDD with full_page_writes=on is interesting. I don't
know why that should happen, and I wonder if there is anything that
can be done to mitigate it.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company