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I have an Ubuntu Server up and running on LVM2 partition. My motherboard supports RAID 0 and 1.

I bought new, second HDD, the same as the system one. I want to set up RAID mirroring to ensure my data are safe.

How can I do this without reinstalling the whole system? Is software RAID better than hardware RAID from cheap motherboards?

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up vote 2 down vote accepted

The general consensus is that motherboard RAID is crud, put in for people who think all buzzwords were created alike. Usually it's proprietary (need to replace your motherboard? You might lose your RAID array), it's lower in performance compared to software RAID, and overall is one of those things that when it works it's okay, when it fails you'll have headaches with no end (unless you make good backups.)

Go software or with a dedicated hardware controller for RAID.

By the way-mirroring isn't a backup. You get a corrupt drive, corrupt software, deletion of something important...instant mirror! Now you have twice the corruption and still lose the file you delete. Keeping your data safe involves making backups.

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I'm already using Bacula for backups. Do I need to reinstall the system, repartition etc. to enable software RAID? The descriptions I've found so far, all are about making new RAID partitions. – takeshin Sep 23 '10 at 15:12
I'd plan on it, as it's supposed to be possible to create RAID sets from existing data in theory, but it's far easier to just plan on creating a blank volume and restore your data than futz with the migration of data. Unless you like the stress and challenge. – Bart Silverstrim Sep 23 '10 at 15:17
What do you mean by saying restore your data? Copy files or some drive image? – takeshin Sep 23 '10 at 20:07
Wipe the computer, create the new RAID volume with software RAID, then run a restore to take data from your backup back to your computer with the new RAID array. – Bart Silverstrim Sep 23 '10 at 20:19
Just make sure your restore doesn't overwrite something that controls your RAID configuration in the process. Personally I keep my data separate (documents, etc.) so I would only have to restore my personal stuff, and in the process it cleans out my computer from older configuration cruft if I install new and configure new. But that's my personal preference. – Bart Silverstrim Sep 23 '10 at 20:21

It's a contentious issue but in general software RAID is much better than hardware RAID from cheap motherboards. I'd simply mirror them in software.

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