At the moment, I'm assuming that since Zimbra installs into /opt, that I need to make sure that /opt is large enough for my (maximum number of users * per-user quota). Currently, I'm looking at 200 megs per user * 2000 users. To be safe, I've created a 500 gig logical volume (Redhat Enterprise Linux 5 as a Xen "guest" on a CentOS 5 "host") for /opt. But... when I was trying to format this file system with ext3, it took a good 40 minutes. (The file system is on a SAN, so I wouldn't expect the performance to be that slow. I did a little reading on Xen and found that disk I/O is a little better when the file systems aren't too large (over 100 gigs let's say). So is it possible for Zimbra to partition it's mail store across multiple file systems? If so, I think that could solve my problem...