I have a 6 device raid 5 array which had 1 disk go bad and then due to a power outage, the machine shutdown and when it started all the disks were showing up as spares with the following mdadm -E output.
/dev/sda5: Magic : a92b4efc Version : 1.2 Feature Map : 0x0 Array UUID : b480fe0c:c9e29256:0fcf1b0c:1f8c762c Name : GATEWAY:RAID5_500G Creation Time : Wed Apr 28 16:10:43 2010 Raid Level : -unknown- Raid Devices : 0 Avail Dev Size : 976768002 (465.76 GiB 500.11 GB) Used Dev Size : 976765954 (465.76 GiB 500.10 GB) Data Offset : 2048 sectors Super Offset : 8 sectors State : active Device UUID : a8499a91:628ddde8:1cc8f4b9:749136f9 Update Time : Sat May 19 23:04:23 2012 Checksum : 9950883c - correct Events : 1 Device Role : spare Array State : ('A' == active, '.' == missing)`
This md device was part a Physical Volume for a LVM Volume Group.
I am trying to recreate the array using mdadm --create --assume-clean using 1 device as missing. I am checking if the device is getting created correctly by checking the UUID of the created device which would match if the device gets created correctly.
I have tried a few combinations of the disk order that I believe is right however I think I'm getting tripped up by the fact that the mdadm I used to create this md device was some 2.x series and now we are on 3.x (and I may have taken some of the defaults originally which I don't' remember) What all 'defaults' have changed over the versions so I can try those? Like chunk size? Can we manually configure the super/data offset? Are those significant when we do an mdadm --create --assume-clean?