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I'm trying to create a RAID 5 array which will contain the Ubuntu installation itself.

I tried this partition scheme:

2.0 TB for /
6.0 GB for swap

This was as per the instructions provided by Ubuntu.

Ubuntu installed successfully until the GRUB step at which it failed with an error that embedding is not supported without a /boot partition (Sorry, I lost the original error).

tl;dr What kind of partition scheme is typically used for bootable softRAID 5?

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1 Answer 1

You can't boot from software RAID5 directly. You should create a small RAID1 array to hold /boot and that should work fine.

I ran Ubuntu off a pair of SD cards in RAOD0 for a while when my netbook's internal SSD died, and all was fine with a small RAID1 array for /boot and the rest on a RAID0 array (it is not possible to boot from software RAID0 either).

edit: make sure you make /boot big enough to hold several kernels and initrds. As you seem to have plenty bit drives this shouldn't be a problem. My home server (which is possibly a pathological case having been Debian/Etch then upgraded to Etch-n-a-half then Lenny and having initially had -686 kernels then -amd64, and has never had such things properly cleared out, so has seven of everything in there) is using 96Mb of it's /boot, so 128Mb should be plenty (I usually go for 200Mb+ for /boot these days except on small SSDs - with the size of modern spinning-disk drives the space isn't missed elsewhere).

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@David: That was true until recently, but Grub 2 has some support for RAID5, and booting from RAID5 is supported since Ubuntu 9.10 according to Ubuntu literature. –  Gilles Aug 17 '10 at 22:52
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@Gilles: +1, I was unaware of that updated support in recent versions. –  David Spillett Aug 18 '10 at 7:43
    
So I should create a /boot partition on all three drives and RAID1 them? –  Austin Aug 18 '10 at 16:17
    
@Austin, yes that is how I normally do it. That way if any of the drives fall out of the array (i.e. one drive dies) you don't find /boot goes missing. Make sure that grub installs its bootloaded onto all three drives (IIRC grub2 detects the need for this so you might find it handled automatically with recent Ubuntu releases). –  David Spillett Aug 18 '10 at 17:14
    
GRUB2 still fails to install (error about embedding) on this configuration. I think I need to have a biosgrub partition not a /boot partition. I also tried GRUB1 and LILO and neither work. Any advice? –  Austin Aug 19 '10 at 16:55

protected by Diago Oct 21 '10 at 20:03

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