On Mon, 2011-07-18 at 22:29 -0400, Michael Orlitzky wrote: > > Make sure your kernel supports RAID, and RAID5 (they're separate > options). Then emerge mdadm. Once you get it up and running once, you > can dump the current config to /etc/mdadm.conf so you don't have to > assemble it again. Then add mdadm to the boot runlevel. > I'm Ok so far - Raid and Raid5 options are both already compiled into the kernel, and mdadm is in the boot runlevel.
> # mdadm --assemble --help > Usage: mdadm --assemble device options... > mdadm --assemble --scan options... > > This usage assembles one or more raid arrays from pre-existing > components. For each array, mdadm needs to know the md device, the > identity of the array, and a number of sub devices. These can be found > in a number of ways. > The md device is either given on the command line or is found listed > in the config file. The array identity is determined either from the > --uuid or --super-minor commandline arguments, from the config file, > or from the first component device on the command line. > > The different combinations of these are as follows: > If the --scan option is not given, then only devices and identities > listed on the command line are considered. > > The first device will be the array device, and the remainder will be > examined when looking for components. > > If an explicit identity is given with --uuid or --super-minor, then > only devices with a superblock which matches that identity is > considered, otherwise every device listed is considered. > > If the --scan option is given, and no devices are listed, then > every array listed in the config file is considered for assembly. > The identity of candidate devices are determined from the config file. > > If the --scan option is given as well as one or more devices, then > Those devices are md devices that are to be assembled. Their identity > and components are determined from the config file. > > If mdadm can not find all of the components for an array, it will > assemble it but not activate it unless --run or --scan is given. To > preserve this behaviour even with --scan, add --no-degraded. Note that > "all of the components" means as many as were present the last time the > array was running as recorded in the superblock. If the array was > already degraded, and the missing device is not a new problem, it will > still be assembled. It is only newly missing devices that cause the > array not to be started. Pardon my additional questions before taking the plunge here. So, given that I have three devices, /dev/sda, /dev/sdb and /dev/sdc, if I run the command mdadm --assemble --scan, would this find all the components and create a /dev/md0 disk without damaging the contents of the original RAID array? The only item in /dev/mapper is th default 'control' entry. There is a /dev/md0 item already listed, but presently when I try to mount it, it reports that it is unable to read the superblock. Would the command above fix this? Where is the config file mentioned in your e-mail, and do I need to edit it first to add the three raid disks? Thanks Jeff
