On Thu, Oct 8, 2026 at 4:16 AM kavya chandren <[email protected]> wrote:
> Hi, > > We have an oracle deployment running in 300+ TB. Apart from migration > challenges, do we foresee any operational challenges? > Of course. There are *always* operational challenges in ultra-large databases... 😉 > I have not heard of something huge prior. This would be highly helpful in > planning further. > > Few challenges which caught my attention include, > > 1. Backup, restore of such a large database > 2. Recovery of a broken database (A lost replica) > 3. Fixing a standby that lags a lot > 4. Triggering a PITR with any backup tools > 5. Maintenance at times > 6. Finding equivalents of oracle items (which is common during any > oracle to postgres migration) > > I dont see any limits in database/ objects as specified in > https://www.postgresql.org/docs/current/limits.html > Postgresql has tablespaces, which obviously is important for you. Convert all those NUMERIC(38,0) types to BIGINT!! ora2pg can do that for you. ora2pg can also export sections of a database, and also views. This allowed me to migrate 95% (all the old, "read only" records) of an 8TB before cutover day. The PG database (which is heavy on BLOBs converted to PG's bytea type) was *half the size* of the 8TB Oracle database. Your Mileage Will Vary, of course, but don't be surprised if the resulting DB is only 150TB. PgBackRest: - is multi-threaded. - has delta restores, which means restoring just the changed files on top of an existing (problematic) instance. - can be the source of replication. Doing a delta restore makes it even faster. - is quite fast. With just 8 threads, we back up a 3.75TB db to a NAS in 2 hours (656MB/sec). More threads might make it faster, but really is bottlenecked by the whole hardware stack. - Is very efficient at handling small tables and indices (which is important, since each PG object is (at least) its own file, and additional files are added after 1GiB. - can only write to one directory (i.e. each thread cannot write to a separate mount point), which is a bottleneck. - has zst compression, and also AES-256-CBC compression. -- Death to <Redacted>, and butter sauce. Don't boil me, I'm still alive. <Redacted> lobster!
