Where do Unix shops who want to migrate go next? You'd think they go for Linux. Or is it Windows? It depends who's asking.

According Microsoft-commissioned research, contrary to what one might see as a natural move over from Unix to Linux, more ex-Unix shops run Windows than Linux.

A survey, conducted by IDC on Microsoft's behalf, looked at 400 Unix shops, which were garnered at random from our sister title Network World's subscriber list, according to one report.

Most of the organisations ran Solaris, although the numbers for that OS were down from the 80 per cent reported in a previous survey to 71 per cent, while the rest ran IBM's AIX (55 per cent), HP's HP/UX (44 per cent) and even Tru64 Unix at 14 per cent.

The numbers for all of the Unix variants were down, and roughly half were either definitely or somewhat likely to move to another OS in the next two years. Half were staying put though, adding weight to the argument that the Unix market doesn't move much because the systems stay up and keep working for years. That said, the SCO and Tru64 Unix users were most likely to move, with the rest remaining more loyal.

In terms of units, Windows will be installed on 44.8 per cent of those replacement servers, but Linux on only 37.1 per cent of them, found the survey.

But then, surveys can never tell you the whole story. According to another report, even the most mission-critical, Unix-based central business systems are being replaced by Linux running on commodity hardware, according to delegates at Linuxworld 2006 conference and expo in Sydney this week.

Maybe things are different down under, but maybe too, the fact that Microsoft commissioned IDC's survey played a part in its outcome. After all, you only ever get the right answers if you ask the right questions.