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On Wednesday 17 May 2006 12:47, Peter Humphrey wrote: |
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> Well, I tried the Software-RAID-HOWTO, and used a SuSE 9.3 DVD I had |
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> lying around to create /dev/md0 to /dev/md5 on the /dev/sd[ab] disks |
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> that are attached to the SATA interface. SuSE installed just fine and |
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> is happy to run on these devices. |
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> |
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> In spite of that, when I boot the Gentoo 2006.0 installation CD and |
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> tell it: |
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> |
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> gentoo dodmraid dmraid=-ay |
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> |
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> It says in the boot sequence: |
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> |
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> Activating Device-Mapper RAID(s) |
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> No RAID disks |
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> |
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> Then when the image has booted, I say fdisk -l and I see the |
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> partitions on /dev/sda and /dev/sdb with no trace of /dev/mdX. |
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> |
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> What am I doing wrong? |
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> |
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> Meanwhile I'll have a play with your scripts, Robert, and see if that |
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> gets me anywhere - thanks. |
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This used to confuse me as well - from what I understand, MD raid (the |
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one you set up with SuSE) and DM raid (the one you are trying to use |
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with gentoo) are very different beasts. MD raid is the classic plain |
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software raid (the one you set up using the software-raid howto), while |
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DM raid (aka ataraid, biosraid, bios-assisted raid, and other similar |
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names) uses the device mapper and is used mainly to be able to use raid |
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volumes (often created under windows) that lie on disks attached to |
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firmware-raid cards. |
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These cards come with drivers (usually windows-only and proprietary) that |
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emulate a hw-raid, so that windows can see the array as a single drive. |
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Nevertheless, it's still an emulated (in software+firmware) hw-raid, |
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meaning that a real os (like linux) will see the single physical drives, |
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unless some kind of workaround (like DMraid) is in place, and even then |
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I would not put my valuable data on it. That's why I (and others as |
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well) suggest using plain MD software raid. |
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|
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See here: |
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http://people.redhat.com/~heinzm/sw/dmraid/readme |
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and, for the gentoo part |
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http://tienstra4.flatnet.tudelft.nl/~gerte/gen2dmraid/ |
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(read the "What can I do with the LiveCD / dmraid?" section) |
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Hope this helps. |
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-- |
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