"is it possible to backup suse (9.1 pro) from one hdd to another? when this hdd crashes, a few
hours work will be lost.
it would be a quite simple solution if i put the new hdd (with the suse backup) in the computer and can continue working."
Yes, it is possible. However don't try to do it by creating disk images with dd. Using dd can cause all kinds of flaky problems which you don't need in a backup/restore scenario. You can use a series of cp commands in a script to copy a working system onto a partition on a seperate hard drive. I do this with the cpbk command which is an archaic program similar to cp. A major advantage to doing it this way is that you can set up the backup to only copy files which have changed, thus cutting down backup time significantly.
In the past I have created a new Linux operating system on a spare drive and then swapped drives to install the new system. About 30 years ago I used to routinely install new OSs that way. But I don't recommend it as a backup/restore method. Instead I recommend that you use cp to create a backup partition on a seperate hard drive. To restore, boot a rescue CD and then copy over enough of the backup system to restore the broken system to working order. If you lose a complete hard drive due to hardware failure you could swap hard drives and then boot a rescue CD to do the work of making the replacement hard drive a working system.