Re: Migration from MSSQL to POSTGRESQL

It really depends on how much of those 64 vCPUs and 250GB RAM your SQL Server actually uses today, and whether you’re running on a physical box or a virtual machine.

PostgreSQL doesn’t have a 1:1 sizing formula against SQL Server. I’d first look at real CPU/memory usage, workload pattern (OLTP vs reporting), and how connections/queries behave. I’d also factor in how well we can migrate and map the data types and queries, because good type choices and query rewrites can significantly reduce resource usage.

• If it’s a physical server, I’d start with similar hardware for PostgreSQL and then tune Postgres parameters (shared_buffers, work_mem, etc.) based on monitoring.

• If it’s a VM, I’d provision a bit more capacity than the current SQL Server allocation to give some headroom for tuning and unexpected overhead, and then right-size after observing the real load in PostgreSQL.

Once the migration is done and in steady use, we can monitor CPU, memory, and I/O in PostgreSQL and then optimise or scale down/up based on real metrics instead of guessing up front.