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CCDCONFIG(8) System Manager's Manual CCDCONFIG(8)

ccdconfig — configuration utility for the concatenated disk driver

ccdconfig [-cv] ccd ileave [flags] dev ...

ccdconfig -C [-v] [-f config_file]

ccdconfig -u [-v] ccd ...

ccdconfig -U [-v] [-f config_file]

ccdconfig -g [-M core] [-N system] [ccd ...]

The ccdconfig utility is used to dynamically configure and unconfigure concatenated disk devices, or ccds. For more information about the ccd, see ccd(4).

The options are as follows:

Configure a ccd. This is the default behavior of ccdconfig.
Configure all ccd devices listed in the ccd configuration file.
config_file
When configuring or unconfiguring all devices, read the file config_file instead of the default /etc/ccd.conf.
Dump the current ccd configuration in a format suitable for use as the ccd configuration file. If no arguments are specified, every configured ccd is dumped. Otherwise, the configuration of each listed ccd is dumped.
core
Extract values associated with the name list from core instead of the default /dev/mem.
system
Use system as the kernel instead of the running kernel (as determined from getbootfile(3)).
Unconfigure a ccd.
Unconfigure all ccd devices listed the ccd configuration file.
Cause ccdconfig to be verbose.

A ccd is described on the command line and in the ccd configuration file by the name of the ccd, the interleave factor, the ccd configuration flags, and a list of one or more devices. The flags may be represented as a decimal number, a hexadecimal number, a comma-separated list of strings, or the word “none”. The flags are as follows:

CCDF_SWAP	0x01		Interleave should be dmmax
CCDF_UNIFORM	0x02		Use uniform interleave
CCDF_MIRROR	0x04		Support mirroring
CCDF_PARITY	0x08		Support parity (not implemented yet)

The format in the configuration file appears exactly as if it were entered on the command line. Note that on the command line and in the configuration file, the flags argument is optional.

#
# /etc/ccd.conf
# Configuration file for concatenated disk devices
#

# ccd           ileave  flags   component devices
ccd0            16      none    /dev/da2s0e /dev/da3s0e

The component devices need to name partitions of type FS_CCD (or “ccd” as shown by disklabel(8)).

An error on a ccd disk is usually unrecoverable unless you are using the mirroring option. But mirroring has its own perils: It assumes that both copies of the data at any given sector are the same. This holds true until a write error occurs or until you replace either side of the mirror. This is a poor-man's mirroring implementation. It works well enough that if you begin to get disk errors you should be able to backup the ccd disk, replace the broken hardware, and then regenerate the ccd disk. If you need more than this you should look into external hardware RAID SCSI boxes, RAID controllers such as the dpt(4) controller, or software RAID systems such as vinum(8).

/etc/ccd.conf
default ccd configuration file

A number of ccdconfig examples are shown below. The arguments passed to ccdconfig are exactly the same as you might place in the /etc/ccd.conf configuration file. The first example creates a 4-disk stripe out of four SCSI disk partitions. The stripe uses a 64 sector interleave. The second example is an example of a complex stripe/mirror combination. It reads as a two disk stripe of da2s0e and da3s0e which is mirrored to a two disk stripe of da4s0e and da5s0e. The last example is a simple mirror. /dev/da2s0e is mirrored with /dev/da4s0e and assigned to ccd0.

# ccdconfig ccd0 64 none /dev/da2s0e /dev/da3s0e /dev/da4s0e \
	/dev/da5s0e
# ccdconfig ccd0 128 CCDF_MIRROR /dev/da2s0e /dev/da3s0e \
	/dev/da4s0e /dev/da5s0e
# ccdconfig ccd0 128 CCDF_MIRROR /dev/da2s0e /dev/da4s0e

When you create a new ccd disk you generally want to label it, using disklabel(8) or disklabel64(8), before doing anything else. Once you create the initial label you can edit it, adding additional partitions. The label itself takes up the first 16 sectors of the ccd disk. If all you are doing is creating file systems with newfs(8), you do not have to worry about this as newfs(8) will skip the label area. However, if you intend to dd(1) to or from a ccd partition it is usually a good idea to construct the partition such that it does not overlap the label area. For example, if you have A ccd disk with 10000 sectors you might create a ‘d’ partition with offset 16 and size 9984.

# disklabel -r -w ccd0s0 auto
# disklabel -e ccd0s0

The disklabeling of a ccd disk is usually a one-time affair. If you reboot the machine and reconfigure the ccd disk, the disklabel you had created before will still be there and not require reinitialization. Beware that changing any ccd parameters: interleave, flags, or the device list making up the ccd disk, will usually destroy any prior data on that ccd disk. If this occurs it is usually a good idea to reinitialize the label before [re]constructing your ccd disk.

dd(1), ccd(4), dpt(4), disklabel(8), disklabel64(8), rc(8), vinum(8)

The ccdconfig utility first appeared in NetBSD 1.1.

September 29, 2016 DragonFly-5.6.1