Sun fssnap snapshots
UNIX Review has an
article giving a nice introduction to Sun's fssnap feature for creating UFS
filesystem snapshots. When I was working with
Network Appliance filers at my last job, the snapshot feature was one of the most
useful tools I'd ever seen. Veritas also
offers snapshots with their VxFS product, but that's nice and expensive and adds quite
a bit of complexity to your systems (especially with their restrictive hostid-based
licensing).