an OS question

[cellio]

While waiting for assorted software updates to install today I found myself wondering... Mac OS and Windows usually need to reboot your machine to install updates. Yet I have, several times, seen Unix machines that I believe were being maintained with uptimes of more than a year. What's the deal? Is Unix just better able to support hot-fixes, or are Unix updates that rare? (Or am I wrong about the maintenance of those machines?) And if it's that Unix is better at updating, why does Mac OS, which is Unix-based, need to reboot so often? Mind, it's definitely better in this regard than when I was running Windows; this is a puzzle, not a rant.

Edit: Thanks for the comments thus far. I now understand more about how Unix is put together, and why Windows is different. Still not sure about Mac OS but comments suggest it could be UI-related (that is, the GUI might be more tied into the OS than is the case on Unix).

Comments

[rjmccall.livejournal.com]

Neat. ksplice looks to be relatively heavyweight compared to MS hotpatching, since it requires briefly halting everything except ksplice; but I doubt it makes much difference in practice; the length of actual downtime should be brief unless it actually needs to update data structures, which is not something MS's hotpatching makes any easier.