virtualization - Moving all internal servers to the cloud

Background

One of my clients is an IT-dependent workflow-driven law firm with about 50 seats. They have been audited by one of their clients (an FSA regulated mortgage lender) and told that their single-site is a threat to business continuity. I have proposed that we partition their business into two bits:

1. Client-side - PCs, monitors, chairs, desks, LAN switches and router and firewall




2. Server-side - The Virtual Machines running Active Directory, Exchange, SQL, SharePoint and other line-of-business apps, "robot" worker machines and Remote Desktop Services (around 14 VMs in total)

The idea is that we can store equipment and put arrangements in place to quickly reproduce at least a reduced-capacity client-side environment at an alternative location, or even have users connect from their homes if required.

The Server-side represents a greater challenge, as it includes services published from their (currently ADSL, soon to be 100 Mbps fibre) IP connection and about 3TB data, not including backups. I have proposed that we move the entire server-side environment out of their current self-hosted on-site server rooms and into a hosted facility. I still want the same level of privacy - this has to be firewalled off from the internet except for the small number of published services, and they would be best served from a web-server VM in a DMZ.

Currently there are two server rooms, each containing one node of a replicated SAN and one Hyper-V cluster host. Coupled with redundant fibre-channel and Ethernet links this means the system will keep running even if a whole server room is lost. I want the hosted server-side environment to be similarly resilient to single data-centre loss.

Basically, I want the security, availability and control I get from local self-hosting, but in the cloud, with geopraphical diversity of at least 30 km. I also don't really want to be buying kit and racking it myself and worrying about hardware lifespan and replacement, backups etc.

Questions

1. Is the replicating SAN and Hyper-V Cluster something I should try to replicate in the data-centre, or do large hosters & cloud providers have other ways of ensuring availability?




2. It looks like Amazon AWS has all the bits necessary (EC2, EBS, S3, VPC, VPN etc), but only one EU data centre. What kind of availability can I expect? E.g. If they have a major outage in their Ireland datacentre (imagine an aircraft landing on it, for example), what will happen to the services hosted there? And what about general reliability issues?




3. Can this be done at all using Windows Azure, Rackspace Cloud, or any other cloud service provide?

Thanks for considering my question.