Hi Monica,
Please, remember to answer to the list or your answer will be
only available to me.
El 11/11/19 a las 14:37, Mónica Gamarra
escribió:
You say ...
1 - we want to have the old version available just in
case newer one gives us any problem.
And also
2 - This server has problems with free disk space
And
3 - And the database needs to be up almost 24x7 (please
describe ALMOST in hours/min/sec and
indicate if it applies to all dbs)
1 and 2 are not compatible for your task. If you can't
solve 2 you've only have pg_upgrade, so, you
will lose old version.
Using pg_upgrade it's possible to have old and new postgres
versions running. You only need minor reconfiguration. Of course,
this is only possible if the --link option is not used, which is
the option that needs less disk space.
I you can solve 2 as you need old version you must have
double the space of PG_DATA.
You have to decide this before building a plan.
Talking about 3, all dba's here this, negotiate.
Your timeline depends on main_db (332 GB). You have to
test pg_upgrade time for this database
in a similar server, and also test pd_dump/pg_restore.
Testing before any change in production environment is a must,
always.
IF databases are not related ... and only in this case you
have another option that is install new version
and migrate or upgrade bid database first and then add
databases db1 to db7 (pg_dump/pg_restore)
one by one to new version (with this you minimize the
amount of disk space you need for pg_upgrade
and downtime).
I've used this strategy before, when upgrading other servers with
databases without the almost-no-downtime needs.
Choices.
A) all with pg_upgrade
- less space needed
- NO old version
Wrong: this is only true if --link option is used. All the servers
I've upgraded by now have both versions available, though the old
one is down most of the time.
B) pg_dump/pg_restore
- you need double disk space
- you will have to versions
- more downtime needed (you need to test it no know how
much)
C) A combination of both - ONLY for desperates
[ dump databases db1 to db7, delete databases db1 to db7
from old version, pg_upgrade main_db, pg_restore db1 to db 7
]
- less space needed
- NO old version
- less downtime for main_db
You have to TEST all plans before.
Good luck!
Thank you for the schematic summary of this options (I' already
knew). You've commented anything about replication option though.
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