[plug] dmraid vs mdadm

[Alexander Hartner]

I am setting up a new system. After partitioning /dev/sda, transferring my partition over to /dev/sdb using

sfdisk -d /dev/sda | sfdisk --force /dev/sdb


And setting up the raid arrays using :

mdadm --create --verbose /dev/md1 --assume-clean --level=1 -e 0.90 --raid-devices=2 /dev/sda1 /dev/sdb1
mdadm --create --verbose /dev/md2 --assume-clean --level=1 -e 0.90 --raid-devices=2 /dev/sda2 /dev/sdb2
mdadm --create --verbose /dev/md3 --assume-clean --level=1 -e 0.90 --raid-devices=2 /dev/sda3 /dev/sdb3

Everything seems OK, however if I reboot all the drive names change to :

cat /proc/mdstat 
Personalities : [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] 
md125 : active (auto-read-only) raid1 sdb1[1] sda1[0]
      262080 blocks [2/2] [UU]
      
md126 : active (auto-read-only) raid1 sdb2[1] sda2[0]
      4194240 blocks [2/2] [UU]
      
md127 : active (auto-read-only) raid1 sdb3[1] sda3[0]
      972305024 blocks [2/2] [UU]
      
unused devices: <none>

While this in itself may not be a problem, after I install my OS (Linux of course) I get a kernel panic. I suspect the kernel panic is due to the kernel not finding the partition I specified in grub.conf and fstab (i.e. : /dev/md1|2|3). 

I have been struggling with mdadm raid for several days now, with little progress to show. dmraid seems to leverage what little support is provided by my onboard RAID controller, which seems like a good think. mdadm seems to just keep both drives in sync with each other without leveraging hardware. I might well be wrong there. So far I only tried mdadm.

Alex


On 03/03/2012, at 09:33 , Marcos Raul Carot Collins wrote:

> Are you installing the OS or are you trying to implement to an extra hard disk 
> after installing?
> 
> I only set it up in Debian at install time (mdadm) and although you need some 
> partitioning background, it is prety easy. Let me know if that's your case and 
> I can guide you.
> 
> I haven't tried in other OSes...
> 
> Cheers,
> 
> Marcos
> 
> On Sábado 03 Marzo 2012 05:17:12 Tim White escribió:
>> On 03/03/12 04:36, Alexander Hartner wrote:
>>> Has anybody got any experience with either / both ? Which one do you
>>> suggest ? I have been trying to configure mdadm for the past week
>>> without success. Should I persist or try dmraid ? Is mdadm really so
>>> much better then dmraid ?
>> 
>> I've never used dmraid (and a quick read suggests it's for "software
>> raid" provided by certain bios).
>> What are you trying to achieve? I have successfully used mdadm many
>> times in the past, both with setting up raid and with repairing NAS's.
>> 
>> Tim
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