Re: pg_dump/pg_restore --jobs practical limit?

[Brad White <b55white@xxxxxxxxx>]

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From: Ron <ronljohnsonjr@xxxxxxxxx>
Sent: Thursday, November 2, 2023 3:01:47 AM
To: pgsql-general@xxxxxxxxxxxxxxxxxxxx <pgsql-general@xxxxxxxxxxxxxxxxxxxx>
Subject: Re: pg_dump/pg_restore --jobs practical limit?

On 11/1/23 15:42, Laurenz Albe wrote:

On Wed, 2023-11-01 at 13:09 -0500, Ron wrote:

I will "soon" migrate some 1+ TB database from Pg 9.6.24 on RHEL 6 VMs to Pg 
14.latest on RHEL 8 VMs.  The VMs have 10Gbps "NICs", SAN-based LUNs managed 
by LVM, and are all on ESX blades.  nproc count on some is 16 and on others 
is 32.

Does anyone have experience as to the point of diminishing returns?

IOW, can I crank them processes up to --jobs=30, will I see no gain -- or 
even degradation -- after, for example, --jobs=24?

This would be for both pg_dump and pg_restore (which would be run on the 
RHEL 8 VM).

Test, test, test.  Theoretical considerations are pretty worthless,

Which is why I asked if anyone has experience.

 and it is easy to measure that.

Not necessarily. Our test systems are way too small (only good enough to validate that the script works correctly), and there's always something (sometimes a lot, sometime just "some") going on in production, whether it's my customer's work, or the SAN (like snapshotting every VM and then copying the snapshots to the virtual tape device) or something else.

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Sure,  but are the new systems busy already?

Ideally you could run tests on them before they are put into production.