Since I had lots of difficulty understanding how to get ccd to work
correctly on the sparc port (only one I'm using netbsd on...), I decided
an example might be useful for other people.  Perhaps it could be cleaned
up and shoved into some documentation some place.


There are three ways to use the concatenated device driver.
    a) mirroring
    b) striping, also called interleaving (write to many disks at once, data
       spread all over.)
    c) concatenated (fill one disk, move to next one, etc.)

I'm going to give one example for the striping and one for concatenated on the
sparc port.

First, the man pages to read and the information to gather from them:
    a) man 4 ccd
       The four important things to get out of this is 
       1) Leave a cylinder free on your disk for the ccd disk label.
       2) Configure the kernel to have "pseudo-device ccd 4".
       3) If you lose a disk on striping or concatenated, the file system is
          gone.
       4) If necessary: "cd /dev; ./MAKEDEV ccd0 ccd1 ccd2 ccd3"
    b) man 8 ccdconfig
       Things that I gathered and retained as useful information.
       1) What I consider useful options:
	  A) ccdconfig -C
	     Use /etc/ccd.conf to create ccd configuration.
	  B) ccdconfig -g
	     Display what ccd's are currently configured.
	  C) ccdconfig -U
	     Unconfigure all ccd devices listed in the /etc/ccd.conf file.
       2) There is a bunch of weird stuff that will only confuse you.
       3) You will probably never understand the right interleave to use
	  for striping.  16 and 32 appear to work well on SCSI devices, and
	  with an 8k filesystem (8*1024/512 bytes/sector = 16).
       4) "ccdconfig -C" is called near the top of /etc/rc -- for rebooting.
       5) It doesn't appear possible to stripe the root or swap partitions.
    c) There isn't anymore, and looking at the file /usr/include/dev/ccdvar.h
       will probably confuse you even more, as will looking at the source
       in /sys/dev/ccd.c.

For a striped disk, the conditions, and procedure I followed (and tested as I
am writing this):
    a) Figure out what disks you want to stripe.
       I've got three six year old cdc wren 6's (660mb 5 1/4" form factor) in
       external cases.  I've got a kernel were the disks are specifically
       associated with their SCSI id's.  Don't want a disk not being powered
       up causing incredible problems.  I.e.:
	  sd0	at scsibus? target 3 lun ?
	  sd1	at scsibus? target 1 lun ?
	  sd2	at scsibus? target 2 lun ?
	  sd3	at scsibus? target 0 lun ?
	  sd4	at scsibus? target 4 lun ?
	  sd5	at scsibus? target 5 lun ?
	  sd6	at scsibus? target 6 lun ?
       The disks are sd0, sd2, sd3.
       A fourth disk is on sd5, but it is an five year old cdc Wren 8 (1.4gb
       5 1/4" form factor).  It has root, swap, and /usr set up for backup
       booting.  The idea of adding this to the striping is to enable
       understanding of what is really going on.
    b) Create /dev/ccd.conf and the disklabels.
       1) This is pretty much a joint step.
	  Since a cylinder must left available for the new ccd label, you
	  can't just use the "c" partition on the disks.  You gotta create
	  another one.
	  A) "disklabel -e sd5"		# complicated one first!  (abbreviated)
	     If it uses "vi", upon saving and exiting [I use ":x"] it checks
	     for somewhat reasonable input.

       bytes/sector: 512    sectors/cylinder: 1305   cylinders: 2116
       8 partitions:
       #       size   offset fstype [fsize bsize  cpg]
	 a:  150075       0  4.2BSD   1024  8192   16	# (Cyl.   0 - 114)
	 b:  130500  150075    swap                  	# (Cyl. 115 - 214)
	 c: 2761380       0 unknown                  	# (Cyl.   0 - 2115)
	 g:  430650  280575  4.2BSD   1024  8192   16	# (Cyl. 215 - 544)
	 h: 2050155  711225  4.2BSD   1024  8192   16	# (Cyl. 545 - 2115)

	  B) Desire to use the "h" partition, but forgot to find out how big
	     a wren 6 really is after it's partitioning.
	  C) "disklabel -e sd0"
	     Get rid of everything but the "c" partition, add a "g" back.
	     Since a cylinder is 795 sectors, the offset on a sun must be 795.
	     1294260-795 = 1293465 (and hence the size of the "g" partition).
	     The fstype seems to need to be set "sometimes".  So I just set all
	     the parameters to reasonable default.  The '# (Cyl.' stuff is
	     just a comment, and need not be set.  Next "disklabel -e sd0"
	     will set them.  If you have a "*" after either of the cylinder
	     numbers, then you blew the calculations and didn't fill up a
	     cylinder.

       bytes/sector: 512
       sectors/track: 53
       tracks/cylinder: 15
       sectors/cylinder: 795
       cylinders: 1628
       rpm: 3600
       interleave: 1
       trackskew: 0
       cylinderskew: 0
       headswitch: 0
       track-to-track seek: 0
       drivedata:0
       8 partitions:
       #       size   offset fstype [fsize bsize  cpg]
	 c: 1294260       0 unknown                  	# (Cyl.   0 - 1627)
	 g: 1293465     795  4.2BSD   1024  8192   16	# (Cyl.   1 - 1627)

	  D) Set up sd2 and sd3 the same way.
	  E) Back to "disklabel -e sd5".  Since the wren 6's are only 1293465
	     worth of useful information for striping, and all disk drives
	     should be the same size, the "h" partition should be shortened to
	     1293465.  (I'm not doing it to see what happens.)
	  F) Check no ccd devices are configured.
	     "ccdconfig -g".
	     no concatenated disks configured.
	  G) Set up /etc/ccd.conf.  Edit and insert:
	     ccd0    16    none   /dev/sd0g /dev/sd2g /dev/sd3g /dev/sd5h
	  H) "ccdconfig -C" to set it up, then "ccdconfig -g" to check it took.

       2) Create the disklabel for the striped disk.
	  "disklabel -e ccd0"
	  You have absolute garbage.  You get to fix it up to something
	  reasonable.  1627 cylinders on a wren 6, times 4 makes it 6508.

       bytes/sector: 512
       sectors/track: 53
       tracks/cylinder: 15
       sectors/cylinder: 795
       cylinders: 6508
       rpm: 3600
       interleave: 1
       trackskew: 0
       cylinderskew: 0
       headswitch: 0
       track-to-track seek: 0
       drivedata:0
       3 partitions:
       #       size   offset fstype [fsize bsize  cpg]
	 c: 5173860       0 unknown                  	# (Cyl.   0 - 6507)

       3) If you get it really wrong, the disklabel program may ask for a "y"
	  to re-edit.  The numbers for sectors, tracks, cylinders are all
	  pretty much not used by "ccd".  Just get everything to match for the
	  calculations.
       4) You could create other partitions, not just a "c" -- but since you
	  are probably trying to get a faster (and bigger ) disk that probably
	  is not desired.
    c) Create the new file system.  "newfs /dev/rccd0c"
       2.5gb ... not bad for old disk drives... .
    d) Mount the new file system.
       "mount /dev/ccd0c /mnt"
       "df /mnt"
       Filesystem  1K-blocks   Used     Avail Capacity  Mounted on
       /dev/ccd0c    2502251      1   2377137     0%    /mnt
    e) Does it work?  "cp /netbsd /mnt/netbsd"    All lights flashing at same
       time.

For a concatenated disk, the conditions, and procedure I followed (and tested
as I am writing this):
    a) Figure out what disks you want to concatenate.
       Read above for striping for kernel associating of SCSI id and disk.
       Disks:
	  sd0	CDC Wren 6  (660mb)
	  sd1   CDC Wren 9 (1897mb)  root, swap, /usr, /usr/src, extra (875mb)
	  sd2	CDC Wren 6  (660mb)
	  sd3	CDC Wren 6  (660mb)
	  sd5	CDC Wren 7 (1413mb) altroot, swap, alt/usr, extra  (1049mb)
	  sd6	Seagate ST12550N (2138mb)
       The disklabel for sd1d shows:
	   bytes/sector: 512   sectors/cylinder: 1440   cylinders: 2574
	   #        size  offset
	      d: 1709280 1997280   4.2BSD   ...... #(Cyl. 1387 - 2573)
       The disklabel for sd5h shows:
	   bytes/sector: 512   sectors/cylinder: 1305   cylinders: 2116
	   #        size  offset
	      h: 2050155  711225   4.2BSD   ...... #(Cyl. 545 - 2115)
    b) Create disklabels on the disks.  "sd1d" and "sd1h" above.
       Number of blocks given for each.
       Create a "g" partition for use in concatenation, as with striping on
       others -- leaving one cylinder free for fake disklabel.
       sd0g	1293465
       sd1d	1709280
       sd2g	1293465
       sd3g	1293465
       sd5h	2050155
       sd6g	4174464
       Total:  11814294 blocks, or 6048.918528mb.
    b) Create /dev/ccd.conf.
       1) Check no ccd devices are configured.
	  "ccdconfig -g".
	  no concatenated disks configured.
       2) Set up /etc/ccd.conf.  Edit and insert:
    ccd0  0  none  /dev/sd0g /dev/sd2g /dev/sd3g /dev/sd6g /dev/sd5h /dev/sd1d
       3) "ccdconfig -C" to set it up, then "ccdconfig -g" to check it took.
    c) Create the disklabel for the concatenated disk.
       "disklabel -e ccd0"
       You have absolute garbage.  You get to fix it up to something
       reasonable.  You need numbers that fit in 16 bits... .
       /usr/games/factor 11814294   gives 2*3*1969049
       /usr/games/factor 11814292   gives 2*2*7*7*7*79*109   which sounds nice.


       bytes/sector: 512
       sectors/track: 79	#  79
       tracks/cylinder: 49	# 7*7
       sectors/cylinder: 3871	# 79*49
       cylinders: 3052		# 109*7*4
       rpm: 3600
       interleave: 1
       trackskew: 0
       cylinderskew: 0
       headswitch: 0
       track-to-track seek: 0
       drivedata:0
       3 partitions:
       #       size   offset fstype [fsize bsize  cpg]
	 c: 11814292       0 unknown                  	# (Cyl.   0 - 3051)

       3) If you get it really wrong, the disklabel program may ask for a "y"
	  to re-edit.  The numbers for sectors, tracks, cylinders are all
	  pretty much not used by "ccd".  Just get everything to match for the
	  calculations.
       4) You could create other partitions, not just a "c" -- but since you
	  are probably trying to get a bigger disk that probably is not desired.
    d) Create the new file system.  "newfs /dev/rccd0c"
       5768.7mb ... not bad for several smaller disk drives.
    e) Mount the new file system.
       "mount /dev/ccd0c /mnt"
       "df /mnt"
       Filesystem  1K-blocks   Used     Avail Capacity  Mounted on
       /dev/ccd0c    5729879      1   5443384     0%    /mnt
    f) Does it work?  "cp /netbsd /mnt/netbsd"    Not all lights flashing at
       same time.