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A while ago (about 6 months) I set up what I thought was hardware RAID 1 in my BIOS (using the Intel Rapid Storage feature). In Windows the Intel storage manager recognised the RAID volume and synced everything across. I have now discovered that my Ubuntu partition was not syncing between the two disks. How can I set it to respect what I now know is fake RAID, and use the disk that it has been using most recently (sda) to synchronise? The only entry under /dev/mapper/ is control. When using the Live CD the RAIDed partitions appear in /dev/mapper.

Update: I am now working with RAID disabled until this is fixed.

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I have now un-raided the two drives. Using the Live CD I corrected the GRUB config on the up-to-date drive and Windows now boots happily off it, but 3.0.0-23 hangs on a blinking cursor screen, all versions of recovery mode kernel panic about the VFS not working, 3.0.0-16 hangs on a purple screen, and previous versions hang after Checking battery state... [OK]. I have fscked the file system, which says it's clean. –  Dylan Jul 31 '12 at 11:07
    
This is sort of no longer the same issue as the original question; shall I make a new question about these kernel problems? –  Dylan Jul 31 '12 at 11:09
    
Given that no one has answered this question, and that your problem is likely to be a consequence of your RAID troubles, I think it's ok to edit your existing question. Though if the way you un-raided the drives goes beyond the answers to the questions I linked, you should instead answer your question to explain how you solved your first problem, and post another question about your second problem. –  Gilles Jul 31 '12 at 11:27
    
All I did with the first problem is remove RAID in the BIOS then chroot from the Live CD and update-grub2. The entire first paragraph is still relevant. My second issue (I think) is related to linux looking for the wrong drive UUID, as specified in the GRUB config, though I have no understanding of how the GRUB config works and how to make it use the correct device, hence the need for a separate question. –  Dylan Jul 31 '12 at 12:19

1 Answer 1

What you have is known as fakeraid as it doesn't have any hardware acceleration at all, it's just a gimmick that moves simple RAID creation out of the operating system and into the firmware. It's only real benefit is sharing the RAID between multiple operating systems, but that also means you're trusting multiple operating systems to update the metadata consistently and not barf on each other. I try to avoid it like the plague.

https://help.ubuntu.com/community/FakeRaidHowto

Should answer all your questions. The original intend supporting this was to help new users migrate from Windows without having to nuke their hard drives. However once you get established, it's probably a good idea to migrate to a more robust raid driven by mdadm or even a HW RAID.

So assuming dmraid is installed, what happens after it scans your disks? Something should show up in /dev/mapper. The intel metadata format is the defacto standard for this, so it should "just work", unless that is the drives are already in use by the operating system. Be sure to reboot after installing dmraid, backing up critical files before hand is also a good idea.

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