On Tue, 2011-07-19 at 09:06 -0400, Michael Orlitzky wrote: > On 07/18/2011 11:08 PM, Jeff Cranmer wrote: > > > > > > 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? > > If you've got the space and time, a backup can't hurt. Using --scan will > make it check the config file, but right now, there's probably nothing > useful in it. This looks like what you want to do to me: > > 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. > > but I'd figure out where that md0 is coming from (below) first. > When I tried mdadm --assemble --scan with nothing uncommented in the configuration file, I got mdadm: No arrays found in config file or automatically. Typing dmesg | grep md0 returned no lines.
There are a couple of lines in dmesg when I run dmesg | grep md:, but they read md: linear personality registered for level -1 md: raid0 personality registered for level 0 md: raid1 personality registered for level 1 md: raid10 personality registered for level 10 md: raid6 personality registered for level 6 md: raid5 personality registered for level 5 md: raid4 personality registered for level 4 md: Waiting for all devices to be available before autodetect md: If you don't use raid, use raid=noautodetect md: Autodetecting RAID arrays md: Scanned 0 and added 0 devices md: autorun... md: ... autorun DONE. I think this means that raid5 is set up correctly in the kernel, but it can't find the raid array. Next I tried adding a line to the config file: DEVICE /dev/sda /dev/sdb /dev/sdc mdadm --assemble --scan returned the same results as before Next, I tried commenting out the previously added DEVICE line, and adding ARRAY /dev/md0 devices=/dev/sda,/dev/sdb,/dev/sdc mdadm --assemble --scan returns something different mdadm: /dev/sdb has no superblock - assembly aborted. > > > 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? > > Depends. Where'd the md0 come from? You probably have something in your > logs or dmesg, unless that device was created manually on your old system. > > > > Where is the config file mentioned in your e-mail, and do I need to edit > > it first to add the three raid disks? > > It's /etc/mdadm.conf. You don't need it to create or use the array, but > you'll want to run mdadm when the machine boots and the config file > tells it what to do. Once the array is working, you can just do, > > mdadm --detail --scan >> /etc/mdadm.conf > mdadm --detail --scan returns no output. Also, I just checked /dev and md0 is now gone from the list. Since there are also /dev/sg0, /dev/sg1 and /dev/sg1, I also tried those instead of /dev/sda, /dev/sdb and /dev/sdc in the ARRAY line, but mdadm --assemble --scan returned no output I tried re-booting, but /dev/md0 is now permanently gone. Does this give you any ideas what I can try next?? Thanks Jeff
