On May 23, 2007, at 19:03, Jason Lixfeld wrote:


On 23-May-07, at 9:23 PM, Doug Hardie wrote:

The criteria for selecting a backup approach is not the backup methodology but the restore methodology.

Excellent point.

Perhaps I'm asking the wrong question, so let me try it this way instead:

I'm looking for a backup solution that I can rely on in the event I have a catastrophic server failure. Ideally this backup would look and act much like a clone of the production system. In the worse case, I'd re-format the server array and copy the clone back to the server, setup the boot blocks, and that would be it.

Ideally this clone should be verifiable, meaning I should be able to verify it's integrity so that it's not going to let me down if I need it.

I'm thinking external USB hard drive of at least equal size to the server array size as far as hardware goes, but I'm lost as far as software goes.

What kind of data are you backing up? If you are backing up the system and your data then you have to be very careful about links. Some backup solutions will copy the files as separate files. When you restore the link is gone. An update to one of the linked files will no longer be seen by the other names. The OS uses a lot of links. If all you are backing up is data, its probably not an issue. I have used both dump and tar successfully. I currently use tar as I have many directories I don't want to backup. Tar requires some care and feeding to handle links properly. It doesn't do it by default. Dump does handle them properly by default. Another option is rsync. The advantage it has is that it only copies the changes in the file. It will run a lot faster than dump or tar which will copy everything each time. You do have to be careful with /dev if you are copying the root partition.

One backup disk is not all that great a safety approach. You will never know if that drive has failed till you try and use it. Then its too late. Failures do not require that the drive hardware has failed. Any interruption in the copy can cause an issue that may not be detected during the backup. Sectors generally don't just go bad sitting on the shelf, but it does happen. That was a significant problem with tapes. Generally 25% of the tapes I used to get back from off-site storage after a month were no longer readable.

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