equal size not large enough for RAID1?

["Lars Täuber" <taeuber@bbaw.de>]

Hallo list,

I'm new to this list. But I came across some strange problems I nowhere found a solution for on the net.
This is our situation:

monosan + duosan:
Linux duosan 2.6.22.17-0.1-default #1 SMP 2008/02/10 20:01:04 UTC x86_64 x86_64 x86_64 GNU/Linux

/proc/cpuinfo:
[...]
processor       : 3
vendor_id       : AuthenticAMD
cpu family      : 15
model           : 65
model name      : Dual-Core AMD Opteron(tm) Processor 2216
stepping        : 3
cpu MHz         : 2412.402
cache size      : 1024 KB
physical id     : 1
siblings        : 2
core id         : 1
cpu cores       : 2
fpu             : yes
fpu_exception   : yes
cpuid level     : 1
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt rdtscp lm 3dnowext 3dnow pni cx16 lahf_lm cmp_legacy svm extapic cr8_legacy
bogomips        : 4825.08
TLB size        : 1024 4K pages
clflush size    : 64
cache_alignment : 64
address sizes   : 40 bits physical, 48 bits virtual
power management: ts fid vid ttp tm stc

SAS controller:
07:00.0 Ethernet controller: MYRICOM Inc. Myri-10G Dual-Protocol NIC (10G-PCIE-8A)


There are 16 SATA drives multipathed connected to each server.
duosan exports its RAID 6 over AoE via qaoed
monosan sees this as etherd/e22.0

monosan# cat /proc/partitions:
   9     4 12697912448 md4
   9     9 12697912312 md9
 152  5632 12697912448 etherd/e22.0


monosan:~ # cat /proc/mdstat 
Personalities : [raid1] [raid0] [raid6] [raid5] [raid4] 
md9 : active raid1 md4[0]
      12697912312 blocks super 1.0 [2/1] [U_]
      
md4 : active raid6 dm-0[0] dm-8[14] dm-7[13] dm-6[12] dm-5[11] dm-4[10] dm-3[9] dm-2[8] dm-14[7] dm-13[6] dm-12[5] dm-11[4] dm-10[3] dm-9[2] dm-1[1]
      12697912448 blocks level 6, 64k chunk, algorithm 2 [15/15] [UUUUUUUUUUUUUUU]



But then this:
monosan:~ # mdadm /dev/md9 -a /dev/etherd/e22.0 
mdadm: /dev/etherd/e22.0 not large enough to join array

The md9 RAID1 was originally built with e22.0 as second drive. I just simulated a connection loss.

Why is this happening? As you can see md9 consists of md4 and e22.0 and both are equal in size: 12697912448 .
How can I debug this? Are there detailed logs anywhere?

Many thanks for any hint.
Lars



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