On Tue, Sep 2, 2014 at 1:33 PM, <m.roth at 5-cent.us> wrote: > >> I haven't used raw devices as members so I'm not sure I understand the >> scenario. However, I thought that devices over 2TB would not auto >> assemble so you would have to manually add the ARRAY entry for >> /dev/md4 in /etc/mdadm.conf containing /dev/sdd and /dev/sdc for the >> system to recognize it at bootup. >> > Yeah. That was one thing I discovered. Silly me, assuming that the mdadm > would create an entry in /etc/mdadm.conf. And this is not something I do > more than once or twice a year, and haven't this year (we have a good > number of Dells with a PERC 7, or then there's the JetStors....). With devices < 2TB and MBR's, you don't need /etc/mdadm.conf - the kernel just figures it all out at boot time, regardless of the disk location or detection order. I have sometimes set up single partitions as 'broken' raids just to get that autodetect/mount effect on boxes where the disks are moved around a lot because it worked long before distos started mounting by unique labels or uuids. And I miss it on big drives. >> But sdd _should_ have the correct data - it just isn't being detected >> as a raid member. I think with smaller devices - or at least devices >> with smaller partitions and FD type in the MBR it would have worked >> automatically with the kernel autodetect. > > Both had a GPT on them, just no partitions. And that's the thing that > really puzzles me - why mdadm couldn't find the RAID info on /dev/sdd, > which *had* been just fine. > > Anyway, the upshot was my manager was rather annoyed - I *should* have > pulled sdc, and put in a new one, and just let that go. I still think it > would have failed, given the inability of mdadm to find the info on sdd. > We wound up just remaking the RAID, and rebuilding the mirror over the > weekend. I think either adding the ARRAY entry in /etc/mdadm.conf and rebooting or some invocation of mdadm could have revived /dev/md4 with /dev/sdd (and the contents you wanted) active. -- Les Mikesell lesmikesell at gmail.com