need help with RAID1 EFI GPT disks

[Michael Butash]

The only time I've used gpt with linux was with a efi-boot-only laptop, 
but prior I can raid the boot sector drive still with software and not 
have to use fakeraid at all for full partition redundancy. Still kind of 
a new concept for a lot of people I think. Ubuntu otherwise happily 
still uses mbr, so was a bit of a curve for me to have to adapt as they 
don't bake their gpt or raid tools well in the initrd or install.

If you raided your /boot and *other* raid volume, I'd say just redo the 
partitions with gdisk and resync the raid which is pretty easy (I have 
to do this somewhat commonly with my ssd's). I can run swap and root 
from lvm on the raid otherwise for full redundancy and easy disk 
rebuilds if/when needed. That keeps failure recovery very easy. Only EFI 
complicates this with crappy non-raidable fat32 partitions needed now 
(eww, thanks microsoft).

My gpt/efi laptop looks much the same with dual ssd's, but has the first 
partition as an identical fat32 partition on each to satiate ubuntu as 
/boot/EFI and /bootEFI1, plus a mdraided /boot second, and crypt volume 
third. If not adding encryption, lvm atop the mdraid pv for a lot more 
flexibility in volume/redundancy restoration among disks. I just rsync 
the stupid efi fat32 disks.

mb at host:~$ lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sdh 8:112 0 111.8G 0 disk
├─sdh1 8:113 0 100M 0 part
│ └─md127 9:127 0 100M 0 raid1 /boot
└─sdh2 8:114 0 111.7G 0 part
└─md126 9:126 0 111.7G 0 raid1
└─spv0 (dm-0) 252:0 0 111.7G 0 crypt
├─vg0-root (dm-1) 252:1 0 2G 0 lvm /
├─vg0-swap (dm-2) 252:2 0 2G 0 lvm [SWAP]
├─vg0-var (dm-3) 252:3 0 2.5G 0 lvm /var
├─vg0-usr (dm-4) 252:4 0 10G 0 lvm /usr
├─vg0-home (dm-5) 252:5 0 32G 0 lvm /home
sdi 8:128 0 111.8G 0 disk
├─sdi1 8:129 0 100M 0 part
│ └─md127 9:127 0 100M 0 raid1 /boot
└─sdi2 8:130 0 111.7G 0 part
└─md126 9:126 0 111.7G 0 raid1
└─spv0 (dm-0) 252:0 0 111.7G 0 crypt
├─vg0-root (dm-1) 252:1 0 2G 0 lvm /
├─vg0-swap (dm-2) 252:2 0 2G 0 lvm [SWAP]
├─vg0-var (dm-3) 252:3 0 2.5G 0 lvm /var
├─vg0-usr (dm-4) 252:4 0 10G 0 lvm /usr
├─vg0-home (dm-5) 252:5 0 32G 0 lvm /home

-mb



On 02/02/2014 08:44 PM, George Toft wrote:
> installed gdisk and it looks like /dev/sdb is damaged, but /dev/sdc is 
> good :) doing a dd on the whole drive to a file on another drive so I 
> have a backup. I'll check back in a couple days when it's done.
>
> Regards,
>
> George Toft
>
> On 2/2/2014 2:58 PM, Matt Graham wrote:
>>>> # fdisk -l | egrep "GPT|dev"
>>>> WARNING: fdisk doesn't support GPT.
>>>> /dev/sdb1 1 267350 2147483647+ ee GPT
>>
>>>> # mdadm --assemble --run /dev/md0 /dev/sdb1
>>>> mdadm: cannot open device /dev/sdb1: No such
>>>> file or directory
>>
>> This is an odd message to get, and probably means that udev didn't 
>> find the device and create it because udev and/or the rescue system's 
>> GPT support is flaking out. Does the kernel in this rescue system 
>> support GPT? "mknod /dev/sdb1 b 8 17" to create it. You may wish to 
>> "mknod /dev/sdc1 8 33" in case the other softRAID-1 disk has better 
>> stuff on it.
>>
>> As other people have said, there should be no need to use mdadm to 
>> assemble an array out of RAID-1 partitions. "mount /dev/sdb1 
>> /mnt/somewhere" should do something useful if the device node and 
>> /mnt/somewhere exist.
>>
>> On 2014-02-02 12:57, Michael Butash wrote:
>>> Use gdisk if/when doing gpt
>>
>> That too. (One day, we will forsake our filesystems and break all 
>> bonds of block devices to get a disk larger than 2T for actual 
>> experience with GPT, but today is *not* this day. This day, we *SOLVE 
>> TECH PROBLEMS!!!1!*)
>>
>
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