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From: Tayyab Fayyaz <[email protected]>
To: Laurenz Albe <[email protected]>
Cc: Raj <[email protected]>
Cc: Pgsql-admin <[email protected]>
Subject: Re: Migration from MSSQL to POSTGRESQL
Date: Mon, 1 Dec 2025 00:27:59 -0800
Message-ID: <CAFVRaQ2zxmVY+zqADEv2hqo9uR6Q-iYn0v2MQ2EKUtv+yRZKsA@mail.gmail.com> (raw)
In-Reply-To: <[email protected]>
References: <CAJk5AtY9E2E3tL3=1zt82LBZK7Q8BkH65BNG=43oa3qWLrPAtg@mail.gmail.com>
	<[email protected]>

Hello Raj,

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.


Tayyab

On Sun, Nov 30, 2025 at 11:14 PM Laurenz Albe <[email protected]>
wrote:

> On Mon, 2025-12-01 at 08:46 +0530, Raj wrote:
> > I am migrating from MSSQL to POSTGRESQL. In MSSQL, I am using 64 vCPU
> and 250GB RAM.
> > Now how much we can give in postgres?
>
> If these specifications worked for you with Microsoft SQL Server, use the
> same
> with PostgreSQL.  If you can, don't use Windows.
>
> Yours,
> Laurenz Albe
>
>
>

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