mdadm: do you still have set fdisk types

Fred Caro · 01-03-2015, 09:02 PM

If you want to setup a raid1 system will modern mdadm programs on debian/ubuntu on a new/zeroed disk automatically set the type to Oxdm ?

Fred.

syg00 · 01-04-2015, 08:23 PM

Partiton types are ony relevant to partitions.
As noted in your closed dupicate thread, mdadm manpage has advice on this - as does the Linux RAID wiki. All easily findable by searching.

Fred Caro · 01-05-2015, 08:20 PM

Thanks for your reply, syg00 and moderator.
I have read that raid wiki, I'm just a bit slow. So I take it that the paritions that are to make up the raid have to be marked as such before mdadm is employed and will not be re-designated by mdadm's 'create' command?

Fred.

rknichols · 01-05-2015, 09:29 PM

Actually, they don't have to be marked (i.e., partition type set to 0xfd) at all. In-kernel RAID autodetection using that partition type worked only with RAID superblock version 0.9 and is now deprecated. Userspace RAID detection, the preferred method, does not rely on partition type. https://raid.wiki.kernel.org/index.php/Autodetect

Ztcoracat · 01-05-2015, 10:19 PM

What is oxdm?

Fred Caro · 01-06-2015, 08:35 PM

sorry, 0xfd. I see there are many options for software raid and 2 drives, of a similar type, bought at the same time would probably fail at a similar time and so raid1 has limitations but a Debian install with separate /boot partitions (to the dm0) on each drive should work? Not using lvm.

slow fred.

Fred Caro · 01-09-2015, 07:22 PM

OK, here goes the question:

I set up raid1 on 2 disks with 2 partitions each (sda sdb, 1+2) both as raid1, md0 and md1.

md0 was /boot on both sda and sdb

md1 was / on both sda and sdb

sda also contained a swap partition outside the raid1 setup

This was a i386 setup done with gparted disk for the partitions and the raid using mdadm --create with a suffix of --metadata=0.90 (similar) as suggested by the program

I set the mount points from the Debian install disk and rebooted,

all was fine.

To simulate a disk, or lead failure, I disconnected the sda ide lead (each drive on individual leads) and the boot process will not find any drive.

I tried to access what was on the drive using 'supergrub2' cd but it found errors when trying to access raid, presumably because grub is only on sda

is there any means of rectifying this without starting again?

Fred.