Pgtune suggest hundreds for effective_io_concurrenc when using NAS about pgtune

[le0pard]

It seems, that it is bad idea and you get much better efficiency putting small value like 2

Where "it seems"?

[aleskinen]

I got much better efficiency using HDD settings. Although network mounted volume is slow it gives similar values than with ssd.

[le0pard]

Although network mounted volume is slow

why it slow? Lets check on AWS:

https://aws.amazon.com/ebs/details/

Max IOPS**/Volume:
EBS Provisioned IOPS SSD (io1) - 32000
EBS General Purpose SSD (gp2) - 10000
Throughput Optimized HDD (st1) - 500
Cold HDD (sc1) - 250

You can also check numbers on Azure and Google Cloud.

[aleskinen]

We have own iscsi disks and at least with them dropping effective_io_concurrency to 2 and raising random_page_cost to 4 gives much better results.

[le0pard]

If you NAS slow - select HDD, it will be correct for your case. SSD can be also slow as HDD, but this settings doesn't mean "worst SSD" or "NAS by 2G speed connection"