Maintaining the same data on two hard drives, without raid

[JonJ678]

Hey. I'm trying to work this one out through virtualbox at present, but perhaps I'm missing something obvious.

I want to have two hard drives, which are as close to identical as possible. Either bootable. This is as a backup, so when I damage one OS too much or if a hard drive fails, I just plug in the other one and continue as before. I don't want raid 1 since I'd like one of the drives to be outside the computer, this isn't exactly offsite but it's still better than both drives on the same controller.

So far, I'm setting up one drive, Imaging the entire thing across to the other from a livecd, then hoping a weekly rsync will keep everything matching. The main concerns are windows not working on the drive being update after rsync, though I've not got as far as trying to boot from it yet. I'm not really sure how to test this idea either.

Presumably some people on here do something similar, how did you proceed?

 

[JonJ678]

Cheers for the replies

I'm afraid I'm trying to do this to a real hard drive, and only testing ideas with virtualbox. Well, I would be if I didn't keep on having to go to work.

lvm looks like it may well be the answer, I will read up on this. I like that approach walls. Perhaps raid 1 with one unplugged is what I want after all, I didn't realise the disks were individually bootable. I'd have to delete the damaged date/partition before connecting the second drive up again to avoid overwriting good with bad, but this is the most promising approach yet. Cheers

 

[JonJ678]

Solid link, appealed to my sense of humour. I didn't realise rsync could leave you with a bootable volume, though the link doesn't really help with that. If initially dd is run, grub will be on both disks. There may be issues with uuid, I'm not sure about that yet.

"Imaging from a livecd" would be with dd, as I'm fond of the command and don't see the need for more exciting software to achieve the same result. Don't mind that it's offline, I'll do it from a different install anyway.

Linux raid can't do this if there's a windows partition, which unfortunately there is. Autocad is not going to work under wine, and it isn't going to be usable in virtualbox, so my hands are tied. The issue is I don't know if rsync can maintain a copy of a windows partition without stopping windows booting from it, and if so what I need to do in terms of options.

The windows vs linux permissions issue still confuses me. As far as I can tell either group completely ignore the permissions of the opponent. So will rsync preserving permissions reliably maintain a working copy of windows? I'm unsure, though testing this.

I suppose I was hoping for a more obvious answer than dd, then rsync, and not backing up windows.