Jonathan Rogers <thatseattleguy@gmail.com> wrote:
> I was trying to set up a simple mirror (ie, software raid 1) under
> OpenBSD 3.8 using CCD and the generic kernel, mirroring the entirety of
> two one-partition disks. This should have been bone-simple but it was
> pretty frustrating. The various net HOWTOs on how to set up a mirror
> with ccd/ccdconfig were less than fully informative (and in some places
> just plain wrong). And it doesn't help when mis-specifying the
> parameters to simple commands like newfs will give you instant kernel
> panics and crash your system hard...

Indeed, OpenBSD is not forgiving when it comes to messing around with
filesystems and drives.

> I'm not sure why this area of the system's not as robust as everything
> else in OpenBSD, but in case it helps others, here's what I found I had
> to do to not get the usual failures and error messages and to make it
> work. (Google bait follows: " inappropriate file type or format /
> CCDIOCSET / error 22 on component 0 / device not configured / write
> error ")
>
> My scheme:
>
> 0) Obviously, get the bios to recognize the two disks (my fault in this
> case, since I had to find the semi-hidden setting to turn on the
> secondary IDE channel in the BIOS). They should both be seen by the
> kernel at boot. FWIW, I've got two Seagate 40GB ide drives, wd0 and
> wd1.
>
> 1) fdisk -i wd0 (ditto for wd1)
> Writes a default partition table on each drive with one slice taking up
> the whole drive.

Okay, better make sure there's nothing on it.

> 2) disklabel -e -d wd0 (ditto for wd1)
> This gets you an "a" partition on each diskthat takes up the whole disk
> (minus the first cylinder). Change the "fstype" field in this first
> partition from "unused" to "4.2BSD". Ignore the "c" partition that
> represents the whole physical disk.

You should be using ccd for ccd devices, see ccd(4) (on a 3.8 system, I
assume it'll be similar for older systems).

Okay, it will not help much - but it's cleaner, and better for forward
compatibility.

> 3) newfs wd0a (ditto for wd1a)
> Make an identical file system on each drive *separately*, not on the
> combined mirror. (Don't ask me why, all I know is this what made it
> work for me.) Use whatever newfs options appeal to you, as long as both
> drives are configured identically.

Should not be necessary. Looks like voodoo to me.

> 4) edit /etc/ccd.conf:
> Mine reads:
> ccd0 16 CCDF_MIRROR /dev/wd0a /dev/wd1a
> (No, I don't know what the interleave factor of "16" does for a mirror
> set, either. I just left it alone.)
>
> 5) ccdconfig -C
> This creates your mirror. Check it's there with ccdconfig -v -g.
> In my case, I got a new disk, /dev/ccd0c, for my troubles.
>
> 6) mount the mirror set and edit /etc/fstab so it's permanent:
> For me, this was done with "mount /dev/ccd0c /archive". My final
> /etc/fstab entry looks like:
> /dev/ccd0c /samba ffs rw,nodev,nosuid,noexec 1 2
> (of course you may have different mount options than these...this is my
> archive backup disk set so I don't expect to be putting executables
> there)
>
> Hope this helps, but if not post your questions to the group, not to me
> - all I know about the subject I've just written here. Good luck.

Now, there's just been a lengthy thread on misc@openbsd.org where some
very knowledgeable fellows, including the RAIDframe maintainer, told
someone who had also just set up a CCD mirror and posted instructions
similar to yours that a) HOWTOs are evil and b) ccd mirroring will eat
your data (so use RAIDframe).

I tend to agree with a) here - your instructions are not wrong, but not
always correct either, and may tempt other to just type them without
understanding them. Additionally, b) is very, very important if your
data is important enough to mirror - it's likely to be important enough
to mirror right, too.

Joachim