[Zope] Backing up Data.fs

I'm currently trying to work out an effective backup solution for my zope servers. My current system involves shutting down the server, copying the zodb, and then starting the server again. This works, but leaves the site down for several minutes. Is it possible to do the equivilant of a sync and remount read-only? Or is it safe to just copy the ZODB from a live site? I'd also like to hear ideas on how others have setup their backup systems. exporting is not an option as my plone sites do not always correctly reimport. -James Davies (jamesd@mena.org.au)