mdadm: /dev/sdb1 not large enough to join array solution

mdadm --manage /dev/md1 --add /dev/sdb1 mdadm: metadata format 00.90 unknown, ignored. mdadm: metadata format 00.90 unknown, ignored. mdadm: metadata format 00.90 unknown, ignored. mdadm: /dev/sdb1 not large enough to join array

md1's first primary member /dev/sda3 has 57394 cylinders while the /dev/sdb1 has 57393 (1 less cylinder) which is why it won't work.

fdisk -l /dev/sda3

Disk /dev/sda3: 472.0 GB, 472081720320 bytes
255 heads, 63 sectors/track, 57394 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x00000000

fdisk -l /dev/sdb1

Disk /dev/sdb1: 472.0 GB, 472081688064 bytes
255 heads, 63 sectors/track, 57393 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x00000000

Disk /dev/sdb1 doesn't contain a valid partition table

The solution is to delete /dev/sdb1 and make the partition the same 57394 cylinders.
fdisk /dev/sdb The number of cylinders for this disk is set to 121601. There is nothing wrong with that, but this is larger than 1024, and could in certain setups cause problems with: 1) software that runs at boot time (e.g., old versions of LILO) 2) booting and partitioning software from other OSs (e.g., DOS FDISK, OS/2 FDISK) Command (m for help): d Selected partition 1 Command (m for help): p Disk /dev/sdb: 1000.2 GB, 1000204886016 bytes 255 heads, 63 sectors/track, 121601 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Disk identifier: 0x000976e6 Device Boot Start End Blocks Id System Command (m for help): n Command action e extended p primary partition (1-4) p Partition number (1-4): 1 First cylinder (1-121601, default 1): Using default value 1 Last cylinder, +cylinders or +size{K,M,G} (1-121601, default 121601): 57395 Command (m for help): wq The partition table has been altered! Calling ioctl() to re-read partition table. Syncing disks.

#even though I'm matching the cylinders the size still ends up being off!
fdisk -l /dev/sdb1 Disk /dev/sdb1: 472.0 GB, 472089913344 bytes 255 heads, 63 sectors/track, 57394 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Disk identifier: 0x00000000 Disk /dev/sdb1 doesn't contain a valid partition table

#but it ends up being a little bigger so it makes mdadm happy
mdadm --manage /dev/md1 --add /dev/sdb1 mdadm: metadata format 00.90 unknown, ignored. mdadm: metadata format 00.90 unknown, ignored. mdadm: metadata format 00.90 unknown, ignored. mdadm: added /dev/sdb1