I've copied the website files from the first storage server to the second - with the "preserve attributes", so that the dates and such would remain the same - and then I resync'd the servers in ISPConfig to ensure that the user / group IDs all match up. I have got the "WebID" option on, so that all user / group IDs begin from 10000. Whilst all the files do have the correct user ID "web54" or "web21" and so forth, the group IDs seem to be all over the place. They're correct for one website, no problem. But another website has a group ID like "10016". A number and not an actual group name. Another one makes no sense at all and says "5005", which isn't in the 10000+ range. I've possibly made some mistake in copying things over or in the syncing of the cluster with ISPConfig. But I don't really see what I've done wrong or how I might rectify this and make ISPConfig fix the group IDs (the user IDs are fine after the resync, though). And, you know, fix it in a more useful way than manually going through all the files and "chown"ing them by hand. Also, does Apache / PHP / suexec care about the group IDs? Because, as I say, the user IDs are correct. So the website files are owned by the right users - it's just that the users are not all in their correct groups (or even groups that exist - as I don't know why one website has a group ownership of "5005").