(ARCH) ISP type 2 architecture

ELSE: some examples of SMTP architectures

Edited by Nicolas HAHN < hahnn@x-itools.com > / < hahnn@erios.org >

---

Top: [SMTP architecture examples] | Previous: [(ARCH) ISP type 1 architecture] | Next: [(ARCH) Use the ELSE in an infrastructure not designed for that]

---

• ISP type 2 architecture with Microsoft Exchange server 2010/2013 farms per customer
  • Context
  • Pros & Cons

ISP type 2 architecture with Microsoft Exchange server 2010/2013 farms per customer

Context

The proposed architecture is exactly the same as the ISP Type 1, so please refer to previous page to get the context and the drawings.

The only one difference is regarding the way the various ELSE servers are configured, considering the Database aspect only, in all ISP's datacenters.

In Type 2 architecture, a unique ELSE server has its PostgreSQL database configured as the Master. All the other ELSE servers in the other datacenters have their PostgreSQL database in Stand-by mode. Streaming Master to Slaves replication is configured.

Pros & Cons

The drawback of Type 1 implementation disappears here. Any messaging server has to send its logs and data only to the ELSE master server.

We use PostgreSQL replication features.

But other drawbacks might have been introduced here:

• all servers in all datacenters have to send their data to the unique ELSE master server. Let's say that you are an ISP having a datacenter in California, and another datacenter in Italy. Then a lot of data for the database replication, have to cross the Atlantic. It's not really efficient and it introduces huge latencies, slowing down the database, and killing your ELSE servers.
• same problem if you granted access to the ELSE to your customers. If your customers are trying to wait web pages and data from a server at 10000 kms, then you will have an issue again.
• if your ELSE master server is down, then a process have to be followed to promote an ELSE stand-by server as new master.
• how to manage switching to another newly ELSE master from the point of view of all your messaging servers in all your Datacenters?

To address most of the above points, it's possible to think to an ISP Type 3 architecture, that would involve PostgreSQL database Multi-Master replication.

Unfortunately, Multi-Master replication is not an existing standard feature of PostgreSQL Community Edition as of today's version 9.3. So, we have to be patient for this replication to be implemented. This feature is available in Postgres Plus Advanced Server 9.3 from EnterpriseDB, via the xDB Replication Server.

With the 2Quadrant modified version of PostgreSQL 9.4 MMR, it's now possible to get a real Multi-Master Replication PostgreSQL solution.

---

Top: [SMTP architecture examples] | Previous: [(ARCH) ISP type 1 architecture] | Next: [(ARCH) Use the ELSE in an infrastructure not designed for that]