On Tuesday July 11, petr@xxxxxxxx wrote: > >>> Hm, what's superblock 0.91? It is not mentioned in mdadm.8. > >>> > >> Not sure, the block version perhaps? > >> > > Well yes of course, but what characteristics? The manual only lists > > 0, 0.90, default > > 1, 1.0, 1.1, 1.2 > > No 0.91 :( > > > AFAICR superblock version gets raised by 0.01 for the duration of > reshape, so that non-reshape aware kernels do not try to assemble it > (and cause data corruption). Exactly. The following will be in the next mdadm - unless someone wants to re-write it for me using shorter sentences :-) NeilBrown diff .prev/md.4 ./md.4 --- .prev/md.4 2006-06-20 10:01:17.000000000 +1000 +++ ./md.4 2006-07-18 10:14:47.000000000 +1000 @@ -74,6 +74,14 @@ UUID a 128 bit Universally Unique Identifier that identifies the array that this device is part of. +When a version 0.90 array is being reshaped (e.g. adding extra devices +to a RAID5), the version number is temporarily set to 0.91. This +ensures that if the reshape process is stopped in the middle (e.g. by +a system crash) and the machine boots into an older kernel that does +not support reshaping, then the array will not be assembled (which +would cause data corruption) but will be left untouched until a kernel +that can complete the reshape processes is used. + .SS ARRAYS WITHOUT SUPERBLOCKS While it is usually best to create arrays with superblocks so that they can be assembled reliably, there are some circumstances where an - 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
