The reason I ask is that I use rsnapshot for backups with a /backups separate raid1 ext3 back-up disk. Unfortunately removing back-ups (happens every 4 hours) takes up to a full hour! rm -rf /backups/server/hourly.5 will take very long, while all it does it removing the hardlinks, since most data is filled with hardlinks.
ZFS is lovely, but I am thinking of BtrFS, XFS or maybe just ext4 for the new backupserver. ZFS is not suitable at all for production in Linux environments, so that's not an option, although it seems by far the best fs. I will be using BackupPC on CentOS or Debian as software instead of rsnapshot this time. I was considering Bacula, but it seems it has no advantages whatsoever over BackupPC, but is harder to configure and requires an agent to be installed.
I would like a FS that deletes hardlinks fast. I don't see why this has to take an hour, since nothing actually happens to the data anyway.
General advice on back-ups is welcome, but I think if I use backuppc, raid1 for back-ups with a file system that is both fast and ready for production, I have a good back-up environment.