The Solution

Sirius re-designed TLC's existing web hosting infrustructure to a virtualised array that provides redundancy, application failover and enables the easy provision of virtual servers, applications and services.

Sirius' support team provide day-to-day management of the new solution.

At its core is Xen, the Open Source virtual machine platform, running on Linux. Xen's paravirtualisation technology allows multiple virtual dedicated servers to be run on top of the host on the same commodity hardware at the same time.

The new infrastructure benefits from a distributed, virtualised storage system built using DRBD, a Linux kernel module often used in high availability clusters.

Put simply, DRBD bears similarities to RAID 1, except that it runs over a network. Each server device has a state, which can be 'primary' or 'secondary'. If the primary node fails, the secondary device switches to primary state and starts the applications there.

If the failed node comes up again, it is a new secondary node and synchronises its data to the primary without service interruption.

Now, even if 75% of the disks were to fail simultaneously, the array's automatic failover keeps users seamlessly connected to TLC's web services without significantly impacting performance.

Switchback occurs after the new disks are installed.