this is obsolete doc -- see http://doc.nethence.com/ instead

CCD (Concatenated disk driver) configuration 

http://pbraun.nethence.com/doc/sysutils_bsd/ccd.html 

http://pbraun.nethence.com/doc/sysutils_bsd/freebsd_gbde.html 

http://pbraun.nethence.com/doc/sysutils_bsd/freebsd_gmirror.html 

http://pbraun.nethence.com/doc/sysutils_bsd/netbsd.html 

http://pbraun.nethence.com/doc/sysutils_bsd/freebsd.html 

On NetBSD 

The driver is activated by default. It has, 

pseudo-device  ccd  4    # concatenated disk devices

into kernel's configuration. 

Some hints to configure the disks' labels, 

disklabel -l | grep ccd

disklabel -e wd0 ==> ccd

disklabel -Ie wd1 ==> a: ccd

disklabel -Ie wd2 ==> a: ccd

Note. manual says offset has to be at least 1 cylinder but it works great without this constrain. 

Automate the whole thing, 

vi /etc/ccd.conf

like, 

ccd0  0  none  /dev/wd0e /dev/wd1a /dev/wd2a

apply, 

ccdconfig -C

Note. check /etc/defaults/rc.conf for a ccd setting example. 

The official CCD documentation, http://www.netbsd.org/docs/guide/en/chap-ccd.html 

On FreeBSD 

Configuration 

Load the CCD module, 

kldload geom_ccd.ko

Write a standard label (initialize) the disk, 

bsdlabel -w ad8 auto

bsdlabel -w ad9 auto

remove "a" and an "e" partition for ccd, 

bsdlabel -e ad8

bsdlabel -e ad9

e.g., 

8 partitions:

  c: 2930277168        0    unused        0     0         # "raw" part, don't edit

  e: 2930277168        0    4.2BSD        0     0

Create the CCD device, 

ccdconfig ccd0 128 0 /dev/ad8e /dev/ad9e

Format it, 

newfs /dev/ccd0c

Print the config, 

ccdconfig -g > /etc/ccd.conf

Note. "ccdconfig -C" is called at boot time (/etc/rc) 

Add the mount point, 

vi /etc/fstab

add, 

/dev/ccd0c              /path       ufs     rw      2       2

Usage 

Configure all ccd devices listed in ccd.conf, 

ccdconfig -C

Note. "ccdconfig -C" is called at boot time (/etc/rc) 

Unconfigure a ccd device, 

ccdconfig -u ccd0

Unconfigure all ccd devices listed in ccd.conf, 

ccdconfig -U

References 

http://www.freebsd.org/doc/en/books/handbook/raid.html