Backup to multiple smaller drives

[NAC]

So I have a 4tb drive and 2 * 2tb drives for backup. Previously I've used Cobian backup and/or Free File Sync. I prefer open source software and it must be non-proprietary - just copy the files. I exclude some folders from backup, I don't mirror the entire drive.

I know of two ways to backup one 4tb drive onto 2 * 2tb drives:
** set the 2tb drive in raid 0. This seems silly - I don't need the speed, and it would double the chance of losing backed up data.
** create individual backup jobs per folder such that each job is about 2tb or less. So Folders A+B+C go onto backup drive 1 and folders D+E+F go onto backup drive 2. This isn't ideal since folder sizes change with time, I may need to occasionally change the backup processes.

Is there another solution? I've read about spanning drives together, but I believe if one drive fails I could lose (a lot?) of data, which again seems against the point of backup.

 

[NAC]

Anyone have thoughts on this?

 

[dealcorn]

In Unix like systems, "tar" permits a backup to span multiple equal sized drives. My unverified recollection is that failure of a single backup drive does not preclude recovery of files stored on other drives. You may specify multiple targets to include or exclude. Wiki reports: "There are multiple third party tools available for Microsoft Windows to read and write these formats."

 

[dave_the_nerd]

Second option works better, yeah.

Not much to think about. If you have a 4TB drive backing up to 2x 2TB, you have to divide up the data somehow. The specifics are up to the backup software/method you're using, but they'll all let you do it. So just pick one and go with it.

 

[stlc8tr]

I use option #1 to backup my RAID. It's too much of a pain otherwise to backup such a large amount of data.

And the odds of my RAID and my backup drives dying at the same time are small enough that I don't worry about it.

 

[Elixer]

Of course, you could make 2 2TB partitions on the 4TB drive, then do backups that way...

 

[AlienTech]

If this dont include operating system files then copying directories would be the safest bet, what I mean by that is all backup programs I have ysed have drive spanning so it fills data to multiple drives but they put that as one large file. Any error and it is much harder to restore those files. But if they are individual files you can copy just the files you need. Drive error and such means you lose a few files only.. And at worst lose the entire drive.. So chances to wasting a lot of time or losing lots of files are minimized.

I only image the boot partition.. Everything else I copy by directory.. I have gone through a lot of drives with hard errors and such but not completely failed drives. But one thing with using a backup program is it keeps track of changed files.. And it only backs up only those changed files after the first backup. I had to play around with directories to find things that change and move all those to a smaller drive so I could use this kind of backup program. But all other data I backup by hand to make it easier for disaster recovery.