Information Services

Technical description

This is a technical description of the virtual hosting service giving information about the technology used and the suitability of the service for applications.

Infrastructure

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

We have servers based in datacentres at King's Buildings and the Central Area utilitising Dell Poweredge servers.

Each server is connected using two bonded 10Gb 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.

Each server is connected via dual fibre channel links to redundant storage fabrics on the Storage Area Network.

Storage is provided from the IS infrastructure storage area network, through redundant storage network connections. The storage platforms have dual redundant controllers with redundant connections to all disks. All storage is presented from RAID'd disks across two tiers of flash and SATA storage.

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 server 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 or complete failure of the storage platforms. 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.

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 IS.

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://virtual-hosting.ed.ac.uk/ui. This provides console access to the virtual machine. The Windows VMware Infrastructure client is no longer recommended and will not be supported in future releases.

Backup

Data backup of virtual machines can be provided using Veeam 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.

Backups not provided for monthly rental

Backups are not provided to services which are rented for monthly periods.

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. Scientific Linux is considered a supported operating system as it is compatible with RedHat Linux.

Virtual Machine Expiry

As a virtual machine approaches the end of the rental period the customer will be automatically alerted by email. Alerts will be generated at appropriate intervals, e.g. three months, one month, one week and three days before the end of the rental period.

Once the rental period has elapsed the virtual machine will 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.