Technical description

Infrastructure

The IS Virtual Hosting Service is deployed on Intel x86 servers and VMware Enterprise software.

We have clusters based in datacentres at King's Buildings and the Central Area.

Each host in a cluster is connected with resilient links to service networks for hosted applications. Additionally, the network links are used for virtual machine management to allow for virtual machines to migrate between different physical hosts and a further two for service consoles.

All the infrastructure is connected via redundant network switches with multiple uplinks to the core network.

Storage is integrated into the cluster appliances and this is commonly referred to as hyperconverged infrastructure.

Redundancy

The virtual hosting service is designed to have no single point of failure with physical redundancy deployed for server, network and storage infrastructure.

The virtual server software supports live migration of virtual machines between the physical servers called hosts. Live migration is automatically performed to balance the server load across available infrastructure. On physical host failure the virtual machine is automatically restarted on another host. During host maintenance or intrusive maintenance of the virtual server software, virtual machines are manually migrated to prevent any interruption to service.

The only events which would cause significant service failure would be complete failure of the data centre, the network, or complete failure of the storage in a cluster. To protect against these events an additional virtual machine can be deployed at the partner site and appropriate server or application technology used to provide disaster recovery.

Any applications which can be run active/active can be hosted on virtual machines running on different sites and load balanced using a software-defined load balancer/application delivery controller.

Networking

Virtual machines can be attached to a default Virtual Hosting service VLAN or attached to a nominated VLAN routed by the core network. By default, virtual machines will be placed within the Virtual Hosting service VLAN, which is protected by the University's core network firewall. Virtual machines in this VLAN will inherit the default ruleset of this VLAN, which can be modified on request.

If the nominated VLAN is protected by a separate firewall then the topology of the local network must be discussed with the Virtual Hosting team to ensure that the virtual machine can be networked to this VLAN. Problems may occur when the firewall's internal and external networks use physically separated switching.

Management

All physical infrastructure and the virtual server software are maintained by Information Services.

All physical infrastructure is monitored and automatic alerts generated to systems staff on any failure.

There is a weekly pre-approved maintenance slot from 12pm until 2pm each Wednesday. This enables physical infrastructure maintenance and maintenance of the underlying virtual server software. Due to the resilience provided by this service there is no loss of service during maintenance.

The customer management of the virtual machine is through the vSphere vCenter web interface at:

• https://kb-vc.is.ed.ac.uk/ or https://at-vc.is.ed.ac.uk/  (either vCentre can be used to manage services in both datacentres)

If you are not connected to the University network EdLAN, you will need to first connect to the University VPN service.

This provides console access to the virtual machine.

Backup

Data backup of virtual machines can be provided using a separate disk-based block-level backup software. This copies block-level changes to remotely held storage nightly. See the availability and entitlement page for details on charging.

Suitability for Applications

Most applications are suitable for hosting in the Virtual Hosting Service. Specific needs and resource sizing can be discussed with the Virtual Hosting team.

Applications which require sustained high storage performance (in particular random I/O), or sustained network throughput require particular consideration. These should be discussed with the Virtual Hosting team.

Applications, or their supporting operating system, which have not been certified to be hosted by the deployed VMware version are deployed at the customer's risk. Operating System compatability can be checked via VMware compatibility matrix. Red Hat Linux and derivatives such as CentOS Stream, Rocky Linux, Oracle Linux and AlmaLinux are considered a supported operating system as it is compatible with Red Hat Linux. Windows Server is compatible.

Virtual Machine Expiry

Once the rental period has elapsed the virtual machine will become eligible to be turned off and a grace period of one month (for monthly rentals one week) will elapse before the virtual machine and its data are removed. We aim to ensure that people have the option to retain their virtual machines or data before any drastic action is taken.