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Diffstat (limited to 'sbin/ccdconfig/ccdconfig.8')
-rw-r--r-- | sbin/ccdconfig/ccdconfig.8 | 65 |
1 files changed, 60 insertions, 5 deletions
diff --git a/sbin/ccdconfig/ccdconfig.8 b/sbin/ccdconfig/ccdconfig.8 index e687ad1..f3aaa4e 100644 --- a/sbin/ccdconfig/ccdconfig.8 +++ b/sbin/ccdconfig/ccdconfig.8 @@ -145,13 +145,67 @@ The component devices need to name partitions of type as shown by .Xr disklabel 8 ). .Sh EXAMPLE -The following command, executed from the command line, would configure ccd0 -with 4 components (/dev/da2e, /dev/da3e, /dev/da4e, /dev/da5e), and an -interleave factor of 32 blocks. -.Bd -unfilled -offset indent -# ccdconfig ccd0 32 0 /dev/da2e /dev/da3e /dev/da4e /dev/da5e +.Pp +A number of ccdconfig examples are shown below. The arguments passed +to ccdconfig are exactly the same as you might place in the +.Pa /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 da2e and da3e which is mirrored +to a two disk stripe of da4e and da5e. The last example is a simple +mirror. /dev/da2e is mirrored with /dev/da4e and assigned to ccd0. +.Pp +.Bd -unfilled -offset +# ccdconfig ccd0 64 none /dev/da2e /dev/da3e /dev/da4e /dev/da5e +# ccdconfig ccd0 128 CCDF_MIRROR /dev/da2e /dev/da3e /dev/da4e /dev/da5e +# ccdconfig ccd0 128 CCDF_MIRROR /dev/da2e /dev/da4e .Ed .Pp +When you create a new ccd disk you generally want to +.Nm disklabel +it 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 filesystems +with newfs, you do not have to worry about this as newfs will skip the +label area. However, if you intend to +.Nm dd +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. +.Pp +.Bd -unfilled -offset +# disklabel -r -w ccd0c auto +# disklabel -e ccd0c +.Ed +.Pp +The disklabeling of a ccd disk is usually a one-time affair. Unlike other +devices, ccd currently requires that you specify partition 'c' when +running disklabel. 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. +.Pp +.Sh RECOVERY +.Pp +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. +.Nm Ccd +uses 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 then this you should look into external hardware RAID SCSI boxes, +RAID controllers such as the +.Nm dpt +controller, or software RAID systems such as +.Nm vinum . +.Pp .Sh FILES .Bl -tag -width /etc/ccd.conf -compact .It Pa /etc/ccd.conf @@ -160,6 +214,7 @@ default ccd configuration file .Sh SEE ALSO .Xr ccd 4 , .Xr rc 8 +.Xr vinum 8 .Sh HISTORY The .Nm |