Re: 15 pg_upgrade with -j

On 5/22/23 18:42, Tom Lane wrote:
> Jeff Ross <jross@openvistas.net> writes:
>> On 5/22/23 5:24 PM, Adrian Klaver wrote:
>>> So is the 1400G mostly in one database in the cluster?
>>>
>> Yes, one big database with about 80 schemas and several other smaller
>> databases so -j should help, right?
> AFAICT from a quick look at the code, you won't get any meaningful
> parallelism unless you have several large DBs and/or several large
> tablespaces.

Hmm.  I'm glad I'm reading this now.

> It looks like the assumption was that issuing link()
> requests in parallel wouldn't help much but just swamp your disk
> if they're all on the same filesystem.
> Maybe that could use rethinking, not sure.

It does need rethinking in the era of VMs and SANs. /var/lib/pgsql/15 is 
going to be on a different LUN from /var/lib/pgsql/9.6 just like 
/var/lib/pgsql/backups is on a different LUN.

-- 
Born in Arizona, moved to Babylonia.