There is a heavily used server, with older debian, and PG11.
The data is more than 1,2 TB.
The PG_Upgrade is not possible because of lesser space and too old debian.
As we see now we have only one way to move this server.
1.) Installing a new server with actual debian.
2.) Installing the newest PG (17) on it.
3.) Stop work on one database. Dump it in the old, restore it in the new and start the work with that. So we can move them one by one.
But this seems to be very hard, because we need to do this through an internet connection, and the data is too much.
The new server isn't in the same data center?
I have a question about it - is there a better way to do this?
For example we make a new cluster element (a read only slave) with newest debian/PG, and use it to move the data in the background (replication). And then we rename it to master. But I don't know if it's possible or not.
Maybe the slaves must be the same version as the master.
The main problem is that debian is too old, and we are afraid to use PG_Upgrade because of too many version differences (11 < 17).
The fear is justified, since collation changes might corrupt text indices.
But maybe you have some good advice, how to do this with less complication.
Users can tolerate short downtimes, but not longer ones.
Logical replication, not physical replication. Works great if there's not many DDL changes.
Another possibility is COPY TO / COPY FROM in chunks. This will work if most of the 1.2TB is inserted, and then never updated or deleted. That way, at cutover, you only need to COPY TO / COPY FROM and dump/restore (which is really a wrapper around COPY TO / COPY FROM) and "pg_restore --section=post-data".
You (hopefully) know your system better than we do, so you'd have to decide which is better.
