best way to duplicate hard drive for backup

we have a system with the following xfs filesystems on 1T hd:
/
/home
/var/lib/vz (2 servers running on separate ips) /data (used for temporary bkps and experiments)

the latter three are backed up to an external hard drive each night

i would like to keep fairly uptodate bkp of this drive in case it crashes. then, i'd just plug in the bkp.

i don't want to use raid especially because it would mean running 2 drives continuously (i presume this would be the case even with the western digital green drives?)

i know i can rebuild the system from the external, but would prefer to have another drive ready to go rather than rebuilding things from the xfs dumps.

so i figured duplicating the first hd and then keeping it uptodate with rsync. i'd still have the xfsdumps on the external as a 3rd bkp for everything other than /.

questions:
1. is my plan an intelligent one?
2. if so, what is the most sensible way of duplicating the first hd?
a) dd?
b) install from scratch and then overwrite with xfs dumps from external?
c) something else entirely?

in friendship,
prad

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sön 2011-10-16 klockan 17:04 -0700 skrev prad:

a) "dd" requires that the filesystem is offline. It duplicates everything on the disk, even all the random stuff on the disk that aren't files.
b) If you have a proper backup schedule this will allow to restore a older system if something broke a few days ago. Please note that /etc/fstab often contains references to the UUID of the file system. You also need to make sure that the bootloader is updated.
c) You can have a working and tested standby and then restore from xfsdump when you need to. You can set "no backup" file system attribute on files and directories that isn't needed to backup.

--
Emil
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