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HELP - boot to raid0 with multiple drives, 1 down SOLVED
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Moriah
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PostPosted: Thu Mar 07, 2013 4:57 am    Post subject: HELP - boot to raid0 with multiple drives, 1 down SOLVED Reply with quote

see https://forums.gentoo.org/viewtopic-t-953486-highlight-.html?sid=532099391b59228532ae83eb41521e9f for the solution.

I am having trouble setting up the init file in an initramfs with the proper mdadm commands to start a RAID-0 3-way mirror. If all 3 drives are up, it works ok, but with a drive down, mdadm will not start the array. I need a way to robustly start the array with any 2, or even any 1 drive working, and the other drive(s) down. I did this once before, years ago, but that was before mdadm, and I don't remember how I did it.

The problem is if one uses RAID-0 for the boot drive, so a dead drive will still let the system boot, one wants the raid array to asemble and start even if drives are down, just so long as there is at least one working drive. I know this ought to be possible; I just don't know how to do it.

I actually boot from a usb stick, and the root filesystem is on the raid-0 3-way mirror. It is also encrypted with luks/cryptsetup, and it is under lvm control, but my problem is getting the raid to start when a drive is down.

Can anybody help me here?
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Last edited by Moriah on Sun Mar 10, 2013 8:58 pm; edited 1 time in total
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frostschutz
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PostPosted: Thu Mar 07, 2013 7:05 pm    Post subject: Reply with quote

I don't follow you.

RAID-0 also known as AID-0 is not redundant whatsoever, so any drive fails the entire thing is gone, because say in a three drive RAID 0 setup, every third chunk of data is suddenly gone.

If you're looking for a three drive setup where any two drives may fail, that's RAID 1 over three drives.
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Moriah
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PostPosted: Thu Mar 07, 2013 7:30 pm    Post subject: Reply with quote

Brain fade on my part. I meant RAID-1. :-(
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Moriah
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PostPosted: Sat Mar 09, 2013 5:09 am    Post subject: Reply with quote

I still do not have an answer to my question. :-(

How do I start a raid-1 array from my init script in my initramfs so that the array will start if at least any one drive is working?
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Moriah
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PostPosted: Sun Mar 10, 2013 8:59 pm    Post subject: Reply with quote

see https://forums.gentoo.org/viewtopic-t-953486-highlight-.html?sid=532099391b59228532ae83eb41521e9f for the solution.
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