Subject: Re: Database migration across different operating systems
To: pgsql-admin@lists.postgresql.org
References: <A740E5D2-34BE-46AA-A9FE-50F510E771EC@gmail.com>
 <20190108090144.rdrtfh6wznoolsww@office.hexack.fr>
From: Achilleas Mantzios <achill@matrix.gatewaynet.com>
Message-ID: <3eef1017-ce4a-5c4a-0217-ff69d705e38f@matrix.gatewaynet.com>
Date: Tue, 8 Jan 2019 11:26:21 +0200
User-Agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:60.0) Gecko/20100101
 Thunderbird/60.3.2
MIME-Version: 1.0
In-Reply-To: <20190108090144.rdrtfh6wznoolsww@office.hexack.fr>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 8bit
Content-Language: en-US
Precedence: bulk

On 8/1/19 11:01 π.μ., Stéphane KANSCHINE wrote:
> Hey !
>
> Le lun.  7 janv., vers 22:51, Natalie Wenz exprimait :
>> We are in an unusual circumstance, where we need to move all of our
>> Postgres 10 databases from their homes on servers running FreeBSD 11
>> with ZFS to servers in another data center running Red Hat Linux 7.6
>> (also with ZFS), with minimal downtime.
>>
>> I understand that the recommended, safest, approach would be to
>> dump/restore. We intend to do that wherever possible.
> It's not anymore since PostgreSQL have logical replication. You can
> initialize you FreeBSD cluster with a pg_basebackup and you follow
> updates with logical streaming.

Hmm, maybe you mean pg_dump --schema-only? I cannot see how taking physical copy with pg_basebackup will help with logical replication. Logical replication has its own initial snapshot phase. Doing a 
pg_basebackup would work if followed by truncating all tables, but that's duplicate work and equivalent to pg_dumpall --schema-only | psql -f -

>
>> However, we have some databases that require high
>> availability/minimal downtime that are also very large. (50 TB, for
>> example)
> With logical replication, is it's permanently up to date in
> miliseconds, you can switch when you want.
>
>> If it helps: The cpu architecture is the same on both hosts, and
>> we’ll be running Postgres with the same version and same build
>> options.
> Your OS or cpu architecture doesn't matter, really :-)
>
> Regards,


-- 
Achilleas Mantzios
IT DEV Lead
IT DEPT
Dynacom Tankers Mgmt