Suppose that you run production machines, where you don't want to haveto reboot things without a bunch of advance planning (or a seriousemergency). One of the things you want to do on such a system is blockkernel updates. On dpkg-based systems, this is called holding a package.

(One way to do it, the one I use, is ' echo pkgname hold | dpkg--set-selections '. ' dpkg --get-selections | fgrep hold ' can then

This is in part a war story.

We've written our own system to handle deploying spares on our ZFSfileservers . One of the decisionswe made was how much activity to have the system start at once,because we already knew that trying to resilver too many mirrorsat once killed performance for everyone. What we decided was thatwe only wanted one resilver to happen at once and further that wewould abort any ZFS scrubs that were in progress if we needed toactivate a spare, because getting a mirror back