On Call Those of a religious bent might want to look away now, or be regaled by the story of a server room seemingly haunted by a demon that really didn't like Windows in this week's On Call column.
The mystery takes place in the early years of this century, when "David" (which is not his name) was toiling away as a hardware engineer for a third-party maintainer.
His story begins with a jaunt to a client in the city of London and a seemingly innocuous request to drop off an IBM ServeRAID CD requested by a customer.
"Apparently," he told us, "their Exchange server wouldn't boot past the POST screen. It would hang with a blinking cursor in the top left-hand corner."
If nothing else, a reminder to cloud refuseniks that on-premises email has its downsides.
The theory was that the RAID configuration was somehow borked, but booting the CD (running Linux) showed that all was well. It must therefore be Windows that had gotten its knickers in a twist.
"A Windows Server CD was procured, and we attempted to boot it to see if it could be recovered," recalled David.
Alas no. Things seemed to boot up OK from the CD but then hung in the same place.
With things starting to sound a bit like a popular Bernard Cribbins song from the 1960s, David began working through the hardware to find the problem. It was obviously Windows accessing some failed RAM or other bit of faulty chippery not used by Linux, right?
"Over the next two days, I replaced every part at least twice," he sighed. "I called every support engineer in the company, then every other engineer hoping someone had an idea and I lost 2kg stressing."
Still Windows refused to boot. The scenario was simple – if there was a valid Windows partition on the RAID, there would be no booting. If there wasn't a partition on the RAID, or if it was on a non-RAID SCSI controller, Windows would boot. "If you started from a blank RAID group, you could load Windows until the first boot off the new partition when it would hang," added David.
Linux was fine, and would boot up in any configuration. Windows, however… not so good.
The hardware passed every diagnostic test David threw at it, but nothing would persuade Windows to behave.
By the end of the second day, David decided to throw in the towel. He returned to the workshop, built a duplicate system (he certainly had enough hardware now), configured the RAID and loaded up Windows. Everything worked.
Everything was still working the following morning when he disconnected it and took the newly built hardware to the customer.
Upon his arrival he was met by the customer's IT manager, who had come up with a theory of his own: "The server had been possessed by a Microsoft hating demon and it needed an exorcism."
Laughing at such a ridiculous suggestion, David popped the new server into the rack and fired it up.
"My completely new [and fully tested] server does exactly the same thing," he told us.
Fortunately for the IT staff preparing to rush out to find the computing equivalent of Father Merrin, the penny dropped for David.
"They had never heard of an earth loop and didn't believe me until I took their old server out of the server room and put it on a desk in the office where it booted without a problem."
"The first time I saw a problem like this," he told us, "we eventually found that the earth connection inside the power supply was corroded and causing high resistance between 0V and earth, which means the potential of the 0V rail changed as the load on the system changed. Something at that point in the boot process was drawing enough current to trigger a fault."
"I will say that in nearly 40 years of being a hardware maintenance engineer," he added, "I have only seen this sort of thing twice and if I hadn't seen the first one, I would probably be calling the exorcist myself."
A swift call was made to get an electrician on site, and Windows server (NT4, David reckoned) happiness was restored.
Ever taken on your own Microsoft (or Linux) demons, only to find some dodgy wiring behind the mask? Send an email to On Call to share your moment of enlightenment. ®