The government's national pandemic flu website, hosted by BT, crashed within four minutes of going live yesterday.
The problem came in spite of prior assertions by the government that the site would be thoroughly tested, and that any glitches would be viewed as "outrageous".
Paul Jones, chief technology officer at the NHS, told Computerworld UK the site runs on a "standard web solution" based around Microsoft web systems and a Microsoft SQL2005 database.
The system runs on HP blades, he said, adding that "additional capacity was provided by adding ... web and database servers to the clusters", as well as improving virtualisation levels on existing servers. BT referred all queries to the DH.
The site shows people information about swine flu, and has a series of questions to enable them to diagnose themselves.
When it went live at 3pm yesterday (Thursday), some 2,600 people tried to access it every second. The site was built to handle 1,200 hits per second. For several hours the site either did not operate at all, or refused to allow some visitors onto the pages.
At 5.30 pm, BT quadrupled the website's capacity, and the website is understood to have worked successfully since then.
A spokesperson at the Department of Health said the site "did not crash" completely. "It experienced unprecedented demand when it went live with 2,600 hits per second, equivalent to 9.3 million hits per hour," the spokesperson said.
The news follows assertions by health minister Andy Burnham that the website would be properly tested before its launch. On Monday he told MPs: "I can confirm ... that the service will go live in England by the end of this week, subject to testing. ... After the launch, people will no longer need to ring their GP."
He continued: "I am sure that if there were any problems or glitches, members of all parties would not hesitate to say that it was outrageous and would criticise us for launching a service that had not been properly tested."
Professor Steve Field, chair of the Royal College of General Practitioners, told the Guardian the most important thing is that "patient safety ... is not at risk" as a result of the problems.