The NHS Blood Transplant Service (NHSBT) has completed a project that began in 1994 to create a centralised national...
The database merges three regional blood databases running a commercial application, Pulse, with an embedded database, Mimer. The Pulse system tracks blood donor information, such as blood types. NHSBT has merged the three regional Pulse databases into a single system, running on a 64-bit Hewlett-Packard Integrity server and HP storage.
Until now, the hardware, software and network infrastructure to build this high performance, highly resilent system, simply was not available. The system has evolved over the years, as older hardware such as HP Alphaservers are replaced by modern Itanium-based equipment.
NHSBT could not risk merging the regional databases together because of the risk of failure. Instead, it developed complex middleware to to link each databases to provide a UK-wide view of the data.
The new system has built-in redundancy, from datacentres to processors, storage arrays, and networks. The redundant system continuously mirrors the live system, which means failover is instantaneous. General manager for IT Neil Hogg stocks on-site spares for IT components that have a high probability of failure such as discs and power supplies.
The single database means blood donors have to register only once. Their details, including blood test data, are accessed centrally, which eliminates the costs of retesting blood when donors give blood in different regions. He says, "We now have a single system, which is faster and gives us more capacity for future growth."
Users at the NHSBT load data from the central database onto a portable hard disc, which they use at blood donor centres equipped with laptop computers. The data is then copied onto an encrypted USB memory stick and uploaded back into the central database.
Colin Butcher, managing director of consultant Xdelta, designed the built-in resilience. Butcher specified two independent Dense Wavelength Division Multiplexing fibre optic networks, supplied by BT, providing 10 Gbps bandwidth each, to connect the two NHSBT datacentre sites. The networks take different routes to the two sites, which reduces the risk of a failure in the service if one link fails.
Less than a week after going live in August, one of the network links was severed when road construction workers accidentally sliced through the fibre. The service remained live and network traffic was routed through the second network without disruption.
NHSBT needed to modify its database server, Mimer, to enable it to restart quickly after a failure. This will allow the core application, Pulse, to be accessed as soon as the server is restarted. Previously restarting would have taken up to an hour, as the system checked the integrity of the database.
Clive Longbottom, service director at analyst Quocirca says, "It looks like a lot of thought has gone into the design."
Hospitals currently place orders for blood over the phone. In the next financial year Hogg is planning to start a project to link hospitals direct to the NHSBT using EDI. He says, "We will be looking at online ordering, similar to Amazon, but for blood."
How NHSBT built high availability
- Two independent wireless area network connections to prevent disruption if a link is severed
- Database rewritten to restart quicky, which minimise disruption when there is a failure
- Rather than use mirroring, the servers are configured as a cluster across two datacentres, which means that the Pulse application is not impacted by any server downtime