On Thursday December 13, [EMAIL PROTECTED] wrote: > Good morning to Neil and everyone on the list, hope your respective > days are going well. > > Quick overview. We've isolated what appears to be a failure mode with > mdadm assembling RAID1 (and presumably other level) volumes which > kernel based RAID autostart is able to do correctly. > > We picked up on the problem with OES based systems with SAN attached > volumes. I am able to reproduce the problem under 2.6.23.9 UML with > version 2.6.4 of mdadm. > > The problem occurs when partitions are aligned on a 64K boundary. Any > 64K boundary seems to work, ie 128, 256 and 512 sector offsets. > > Block devices look like the following: > > --------------------------------------------------------------------------- > cat /proc/partions: > > major minor #blocks name > > 98 0 262144 ubda > 98 16 10240 ubdb > 98 17 10176 ubdb1 > 98 32 10240 ubdc > 98 33 10176 ubdc1 > --------------------------------------------------------------------------- > > > A RAID1 device was created and started consisting of the /dev/ubdb1 > and /dev/ubdc1 partitions. An /etc/mdadm.conf file was generated > which contains the following: > > --------------------------------------------------------------------------- > DEVICE partitions > ARRAY /dev/md0 level=raid1 num-devices=2 > UUID=e604c49e:d3a948fd:13d9bc11:dbc82862 > --------------------------------------------------------------------------- > > > The RAID1 device was shutdown. The following assembly command yielded: > > --------------------------------------------------------------------------- > mdadm -As > > mdadm: WARNING /dev/ubdc1 and /dev/ubdc appear to have very similar > superblocks. If they are really different, please --zero the superblock > on one > If they are the same or overlap, please remove one from the > DEVICE list in mdadm.conf. > ---------------------------------------------------------------------------
Yes. This is one of the problems with v0.90 metadata, and with "DEVICE partitions". As the partitions start on a 64K alignment, and the metadata is 64K aligned, the metadata appears look right for both the whole device and for the last partition on the device, and mdadm cannot tell the difference. With v1.x metadata, we store the superblock offset which allows us to tell if we have mis-identified a superblock that was meant to be part of a partition or of the whole device. If you make your "DEVICE" line a little more restrictive. e.g. DEVICE /dev/ubc?1 then it will also work. Or just don't use partitions. Make the arrat from /dev/ubdb and /dev/ubdc. NeilBrown - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
