Re: Assistance Needed: Issue with pg_upgrade and --link option

On 28.06.23 12:46, Laurenz Albe wrote:
> On Wed, 2023-06-28 at 15:40 +0530, Pradeep Kumar wrote:
>>>> I was under the impression that the --link option would create hard links between the
>>>> old and new cluster's data files, but it appears that the entire old cluster data was
>>>> copied to the new cluster, resulting in a significant increase in the new cluster's size.
>>>
>>> Please provide some numbers, ideally
>>>
>>>    du -sk <old_data_directory> <new_data_directory>
>>
>> du -sk ~/pradeep_test/pg_upgrade_testing/postgres_11.4/master ~/pradeep_test/pg_upgrade_testing/postgres_14/new_pg
>> 11224524 /home/test/pradeep_test/pg_upgrade_testing/postgres_11.4/master
>> 41952 /home/test/pradeep_test/pg_upgrade_testing/postgres_14/new_pg
> 
> That looks fine.  The files exist only once, and the 41MB that only exist in
> the new data directory are catalog data and other stuff that is different
> on the new cluster.

Interesting, so it actually does count files with multiple hardlinks 
only once.