OpenBSD 5.1 installation on softraid(4)

OpenBSD 5.1 brings new cool features like this one:

"boot(8/amd64) is teached how to access softraid(4) volumes, which allows a kernel to be loaded from a softraid RAID 1 volume. Furthermore it is sufficient to only boot from a disk that is a member of a bootable softraid volume, as this case will be detected and the boot will automatically be redirected to sr[0-9]a:/bsd."

This mean that the bootloader can boot directly from a softraid(4) partition: No more "standard" partitions needed with kernel copied on them on both hard drive!


Here is how to proceed:
During your CD-ROM boot, check that you have a minimum of 2 hard drives detected:

CD-ROM: E0

Loading /5.1/AMD64/CDBOOT

probing: pc0 com0 mem[639K 126M a20=on]

disk: hd0+* hd1+* cd0

>> OpenBSD/amd64 CDBOOT 3.16

boot>

Continue the boot process and select to launch a shell:

Welcome to the OpenBSD/amd64 5.1 installation program.

(I)nstall, (U)pgrade or (S)hell? s

Display the names of the disks detected by OpenBSD:

# sysctl hw.disknames

hw.disknames=wd0:7922594e8158ee03,wd1:49129150e28daf19,cd0:,rd0:7c8ac10ea613493f

On this example (Virtualbox VM), we've got 2 SATA hard-drives: wd0 and wd1 (cd0 is the CD-ROM and rd0 is the RAM drive created by the kernel).
By default OpenBSD create only one /dev for the first hard drive, we need to create a second and initialize a MBR to them:

# cd /dev/

# sh MAKEDEV wd1

# fdisk -iy wd0

Writing MBR at offset 0.

# fdisk -iy wd1

Writing MBR at offset 0.

Now, we need to create a BSD label named "raid" to both disks.
We will create a BSD label for the first drive, and dump/restore the label table to the second drive:

# disklabel -E wd0

Label editor (enter '?' for help at any prompt)

> a a
offset: [64]
size: [20964761]
FS type: [4.2BSD] raid
> q
Write new label?: [y] 

# disklabel wd0 > protofile

# disklabel -R wd1 protofile

Now we can create a softraid(4) volume using the two "a" partitions :

# bioctl -c 1 -l wd0a,wd1a softraid0 

sd0 at scsibus1 targ 1 lun 0: SCSI2 0/direct fixed
sd0: 10236MB, 512 bytes/sector, 20964233 sectors
softraid0: SR RAID 1 volume attached as sd0

This will create a new drive: sd0 in this example.
Return back to the OpenBSD installer (Ctrl+D), and select this new softraid disk for the destination root disk:

# ^D

erase ^?, werase ^W, kill ^U, intr ^C, status ^T

Welcome to the OpenBSD/amd64 5.1 installation program.
(I)nstall, (U)pgrade or (S)hell? i

(etc...)

Available disks are: wd0 wd1 sd0.
Which one is the root disk? (or 'done') [wd0] sd0

Once installed, simply reboot and enjoy:

>> OpenBSD/amd64 BOOT 3.18
boot>
booting sr0a:/bsd: 5648376+1600524+932384+0+616448 [89+497880+322605]=0xd2d0a8
entry point at 0x1001e0 [7205c766, 34000004, 24448b12, ccb8a304]

(etc...)

sd0 at scsibus2 targ 1 lun 0: SCSI2 0/direct fixed
sd0: 10236MB, 512 bytes/sector, 20964233 sectors
root on sd0a (f7748118e1f577a4.a) swap on sd0b dump on sd0b
Automatic boot in progress: starting file system checks.
(etc...)