On Wed, 18 Apr 2012 00:42:54 +0200 John Crisp <john@xxxxxxxxxxxxxx> wrote: > Hi, > > Sorry to trouble people, and I am sure you have better things to do, but > I can't find an answer to the following and don't know where else to go. > > I have been struggling with this problem for weeks and having read all I > can I still don't know the answer. > > I have a server running a version of CentOS 5.x Yes, mdadm is old at > 2.6.9 but it isn't possible to update it currently. > > A year or so ago I clean installed with a software RAID 1 array using > /dev/sda & /dev/sdb and two partitions, md1 & md2 configure > automatically on install. > > I restored data to the RAID and then added manually added a third drive > /dev/sdc as a spare. > > All appeared hunky dory, but whilst trying to figure a slightly > different problem on a different machine, I went back to the first one > to check how it was configured. Although I am sure all looked normal > when I had last looked, this time is looked a bit strange. > > Unfortunately I don't have an exact copy of things before I started > messing about but it looked something like this : > > > cat /proc/mdstat revealed : > > Personalities : [raid1] > md1 : active raid1 sdc1[2] sdb1[1] sda1[0] > 104320 blocks [3/3] [UUU] > > md2 : active raid1 sdc2(S) sdb2[1] sda2[0] > 244091520 blocks [2/2] [UU] > > unused devices: <none> > > > I don't understand how md1 shows [UUU] ?? You have a RAID1 with 3 devices. What it difficult to comprehend about that. Each block is written to all three devices. You don't want that? Change it. mdadm --grow /dev/md1 --raid-disks=4 now it has 4 devices - though one will be missing. mdadm --grow /dev/md1 --raid-disks=2 now it has 2 devices. Actually that won't work until you mark one of the devices as failed, so mdadm /dev/md1 --fail /dev/sdc1 mdadm --grow /dev/md1 --raid-disks=2 But maybe you really wanted a 3-disk RAID1 before - it is a configuration that certainly has a place. Next you'll be telling me that a RAID5 cannot be made with just 2 devices! :-) NeilBrown > > > On my other machine which has a similar configuration it shows the > following which I expect : > > Personalities : [raid1] > md1 : active raid1 sda1[2](S) hdc1[1] hda1[0] > 104320 blocks [2/2] [UU] > > md2 : active raid1 sda2[2](S) hdc2[1] hda2[0] > 312464128 blocks [2/2] [UU] > > unused devices: <none> > > I thought I could fail and remove the drive, dd/fdisk/reformat, sfdisk > and then try to re add it back to the array effectively as a new drive. > No joy. > > If I just fail and remove it md1 shows as [UU_] > > I have tried checking mdadm.conf which has the following : > > DEVICE partitions > ARRAY /dev/md1 level=raid1 num-devices=2 > uuid=8833ba3d:ca592541:20c7be04:42cbbdf1 spares=1 > ARRAY /dev/md2 level=raid1 num-devices=2 > uuid=43a5b70d:9733da5c:7dd8d970:1e476a26 spares=1 > > Somewhere along the line the RAID is remembering the earlier > configuration but having changed stuff left right and Cambridge, I can't > seem to get it to forget. > > I have tried different variations of mdadm.conf, and tried to rebuild > initrd but that didn't fix it and I am clean out of ideas where to go > next. mdadm.conf seems to be ignored. > > Undoubtedly it will take some clever tweaking and I'm scared witless at > trashing the array as I am in a different country from the hardware and > would struggle to get back to fix it ! > > Any advice on how to put it back to RAID 1 with a 'hot' spare would be > appreciated. > > B. Rgds > John > -- > 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
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