On Sat, Dec 20, 2008 at 12:16:01PM +1100, NeilBrown wrote: > On Sat, December 20, 2008 11:34 am, Jon Nelson wrote: > > As part of the output from --explain (on a raid1 with a 1.0 metadata), > > I see this: > > > > Array Slot : 3 (failed, failed, 0, 1) > > Array State : uU 2 failed > > > > I read the first line as "This device is using slot 3. slot 0 is > > failed, slot 1 is failed, slot 2 is RaidDevice 0, slot 3 is RaidDevice > > 1" where RaidDevice is the same as in the output for --detail. Is that > > correct? > > > > The second line is more opaque. What to little-u and big-u mean? Does > > "2 failed" mean the raid thinks two devices have failed? > > > > Yes, it is rather cryptic... > > Every device in a 1.x array is assigned a 'slot' number. This number is > stable - it never changes. > > Each device in the array also has a 'role' number indicating its current > role in the array, which is either to be a spare or to have a position > (0, 1, ...) in the array. > > The output you produces says that this device occupies slot 3. > It then notes that: > the device which occupied slot 0 has failed > the device which occupied slot 1 has failed > the device which occupies slot 2 has role 0 > the device which occupies slot 3 has role 1 > > Then it shows you the state which indicated how the different > roles are going. > uU > means that both roles are 'up', and the 'this' device has the second > role (capital U for 'this' device). > Two devices have previously failed. > > I should probably get rid of that '2 failed' bit, it isn't helpful. > I should probably report 'empty' rather than 'failed' in the 'Array Slot' > line. > > Note that if you fail a devices, remove it, then add it back in such that > it doesn't appear to be a re-add, it will be treated like a new > device and get a new slot number. (after all the old device was faulty, > this one isn't so it must be a new device ?). > I should probably get it to re-use the slot number in that case. > > And I should probably document some of this. Oh, well, you just did :-). I added this to the mdadm FAQ wiki page. keld -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
