Application Hosting
Smaller Deployment
At Six Degrees Group, we acknowledge that cloud hosting is an esoteric topic. Customers are familiar with how to manage their applications, in a physical server environment, on their own premises. However, moving to a virtualised deployment in a cloud model is often unfamiliar. To help with understanding, we have outlined two scenarios below, both for Exchange email.
The first scenario is for a 50 Exchange users with a single-zone deployment on a virtual private cloud.
The first thing to note in this is that, by virtue of being in a purpose-built cloud hosting environment, the application is both Internet-facing and private network-facing. It is for this reason alone that many companies are looking to cloud hosting for their enterprise applications. Secure, high-speed and private network connectivity is available to customer site(s) for access via LAN/W-LAN but Internet access options – e.g. smartphones, tablets, browsers – are also available. Access is, naturally, firewalled.
The deployment is a simple two virtual machine setup. The first VM contains the client access, hub transport and mail box servers (e.g. the elements that make up a simple Exchange scenario). The second VM contains the customer’s Active Directory. And that, simply put, is that. 6DG would deliver this as a fully managed service, end-to-end, with 100% SLA, allowing the customer to focus on running their business.
The second scenario is significantly more complicated. Here we have a 500 Exchange user deployment with 100 “protected” users – e.g. critical members of staff – being fully replicated in a second zone in the event of catastrophic outages in the first zone.
Larger Deployment
As you will see, there are many similarities with the 50 user scenario above, but it is more complicated by an order of magnitude. Again, it is a virtual private cloud deployment but dual-zone instead of single-zone. Similarly, virtual IP traffic would appear to the zone via Internet or Private Network and hit the customer firewall. This time, traffic levels would require load balancing.
Zone 1 features five virtual machines. VM1 contains Active Directory and File Witness Server. VM2 and VM3 are twins with identical Client Access Server and Hub Transport Server instances. VM4 contains Mail Box Server 01, Database Availability Groups 01 & 03, and mirrored backups of DAGs 02 & 04. VM5 contains MB 02, DAGs 02 & 04, mirrored backups of DAG 01 & 03. As you can see, even though Zone 1 houses five virtual machines, it’s already a highly resilient, high availability configuration. The 100 protected users reside on DAG 02.
Zone 2 contains failover servers that will take over in the event of a complete outage at Zone 1 or a complete access network failure to Zone 1 (both highly unlikely). VM6 and VM7 hold the failover Client Access, Hub Transport and File Witness Servers. VM8 contains the third Mail Box Server instance and another failover for DAG 02. In other words, the critical users are protected through two failsafe mechanisms, one in a completely different physical location.
It could be argued that the origins of cloud hosting lie in web hosting. There are several very simple reasons why the vast majority of companies do not want to host their own website: it has to work, all the time, at very high speeds, to be accessed by any user, from anywhere, using any device, and the customer did not want to handle that challenge themselves. Increasingly, this is precisely what companies want for their application hosting – e.g. they still manage the application and the users but somebody else is responsible for keeping it running reliably, quickly and accessibly.