I am running a RAID 6 array under mdadm with 4 x 8TB disks. This array
was working just fine until I rebooted, at which point my array came
back in "auto-read-only" mode, with two devices missing. Upon
inspection, two devices had lost their superblock. I added them back
into the array, and rebooted again, and experienced the same results.
I came across a post online where a user stated that their motherboard
was responsible for this issue, and that upon replacing it, they no
longer experienced the problem.
Another user reported that by switching from block devices (e.g.
/dev/sda, /dev/sdb) to partition (e.g. /dev/sda1, /dev/sdb1), their
issue went away.
I am planning to create a new RAID array using partitions on these
four disks but am looking into insight as to why this is happening (on
only two of my four disks no less) and any methods I can use to debug
this further.
I've included output of mdadm --examine pre- and post-reboot below.
Thanks,
John
jmaguire@Acheron [11:09:50 PM] [~]
-> % sudo mdadm --examine /dev/sda
/dev/sda:
Magic : a92b4efc
Version : 1.2
Feature Map : 0x1
Array UUID : f4951bb9:deb3a188:3ead3067:3fa26009
Name : Acheron:0 (local to host Acheron)
Creation Time : Sat Dec 2 00:14:52 2017
Raid Level : raid6
Raid Devices : 4
Avail Dev Size : 15627791024 (7451.91 GiB 8001.43 GB)
Array Size : 15627790336 (14903.82 GiB 16002.86 GB)
Used Dev Size : 15627790336 (7451.91 GiB 8001.43 GB)
Data Offset : 262144 sectors
Super Offset : 8 sectors
Unused Space : before=262064 sectors, after=688 sectors
State : clean
Device UUID : f6c07805:f704721c:c461c294:35e59e06
Internal Bitmap : 8 sectors from superblock
Update Time : Sat Feb 17 22:40:42 2018
Bad Block Log : 512 entries available at offset 40 sectors
Checksum : b454871f - correct
Events : 146174
Layout : left-symmetric
Chunk Size : 512K
Device Role : Active device 0
Array State : AAAA ('A' == active, '.' == missing, 'R' == replacing)
jmaguire@Acheron [11:09:52 PM] [~]
-> % sudo mdadm --examine /dev/sdb
/dev/sdb:
Magic : a92b4efc
Version : 1.2
Feature Map : 0x1
Array UUID : f4951bb9:deb3a188:3ead3067:3fa26009
Name : Acheron:0 (local to host Acheron)
Creation Time : Sat Dec 2 00:14:52 2017
Raid Level : raid6
Raid Devices : 4
Avail Dev Size : 15627791024 (7451.91 GiB 8001.43 GB)
Array Size : 15627790336 (14903.82 GiB 16002.86 GB)
Used Dev Size : 15627790336 (7451.91 GiB 8001.43 GB)
Data Offset : 262144 sectors
Super Offset : 8 sectors
Unused Space : before=262064 sectors, after=688 sectors
State : clean
Device UUID : 15e0bd42:73869540:2e900fe9:e93d7b09
Internal Bitmap : 8 sectors from superblock
Update Time : Sat Feb 17 22:40:42 2018
Bad Block Log : 512 entries available at offset 40 sectors
Checksum : 6ce6aed7 - correct
Events : 146174
Layout : left-symmetric
Chunk Size : 512K
Device Role : Active device 2
Array State : AAAA ('A' == active, '.' == missing, 'R' == replacing)
jmaguire@Acheron [11:09:53 PM] [~]
-> % sudo mdadm --examine /dev/sdbc
mdadm: cannot open /dev/sdbc: No such file or directory
jmaguire@Acheron [11:09:53 PM] [~]
-> % sudo mdadm --examine /dev/sdc
/dev/sdc:
Magic : a92b4efc
Version : 1.2
Feature Map : 0x1
Array UUID : f4951bb9:deb3a188:3ead3067:3fa26009
Name : Acheron:0 (local to host Acheron)
Creation Time : Sat Dec 2 00:14:52 2017
Raid Level : raid6
Raid Devices : 4
Avail Dev Size : 15627791024 (7451.91 GiB 8001.43 GB)
Array Size : 15627790336 (14903.82 GiB 16002.86 GB)
Used Dev Size : 15627790336 (7451.91 GiB 8001.43 GB)
Data Offset : 262144 sectors
Super Offset : 8 sectors
Unused Space : before=262064 sectors, after=688 sectors
State : clean
Device UUID : 532fc66d:27e98d88:02683729:8886aab8
Internal Bitmap : 8 sectors from superblock
Update Time : Sat Feb 17 22:40:42 2018
Bad Block Log : 512 entries available at offset 40 sectors
Checksum : cf3e813f - correct
Events : 146174
Layout : left-symmetric
Chunk Size : 512K
Device Role : Active device 1
Array State : AAAA ('A' == active, '.' == missing, 'R' == replacing)
jmaguire@Acheron [11:09:55 PM] [~]
-> % sudo mdadm --examine /dev/sdd
/dev/sdd:
Magic : a92b4efc
Version : 1.2
Feature Map : 0x1
Array UUID : f4951bb9:deb3a188:3ead3067:3fa26009
Name : Acheron:0 (local to host Acheron)
Creation Time : Sat Dec 2 00:14:52 2017
Raid Level : raid6
Raid Devices : 4
Avail Dev Size : 15627791024 (7451.91 GiB 8001.43 GB)
Array Size : 15627790336 (14903.82 GiB 16002.86 GB)
Used Dev Size : 15627790336 (7451.91 GiB 8001.43 GB)
Data Offset : 262144 sectors
Super Offset : 8 sectors
Unused Space : before=262064 sectors, after=688 sectors
State : clean
Device UUID : 8ccceef1:d1daefc5:c223a66d:6b39b231
Internal Bitmap : 8 sectors from superblock
Update Time : Sat Feb 17 22:40:42 2018
Bad Block Log : 512 entries available at offset 40 sectors
Checksum : 4e3f7ec4 - correct
Events : 146174
Layout : left-symmetric
Chunk Size : 512K
Device Role : Active device 3
Array State : AAAA ('A' == active, '.' == missing, 'R' == replacing)
jmaguire@Acheron [11:10:07 PM] [~]
-> % sudo reboot
jmaguire@Acheron [11:10:46 PM] [~]
-> % Connection to 192.168.1.14 closed by remote host.
Connection to 192.168.1.14 closed.
jmaguire@scorpion [11:10:46 PM] [~]
-> % ssh 192.168.1.14
Last login: Sat Feb 17 23:09:19 2018 from 192.168.1.28
manpath: warning: $MANPATH set, ignoring /etc/man_db.conf
jmaguire@Acheron [11:17:39 PM] [~]
-> % cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4]
md0 : active (auto-read-only) raid6 sdb[2] sdd[3]
15627790336 blocks super 1.2 level 6, 512k chunk, algorithm 2 [4/2] [__UU]
bitmap: 0/59 pages [0KB], 65536KB chunk
unused devices: <none>
jmaguire@Acheron [11:17:43 PM] [~]
-> % sudo mdadm --examine /dev/sda
[sudo] password for jmaguire:
/dev/sda:
MBR Magic : aa55
Partition[0] : 4294967295 sectors at 1 (type ee)
jmaguire@Acheron [11:17:52 PM] [~]
-> % sudo mdadm --examine /dev/sdc
/dev/sdc:
MBR Magic : aa55
Partition[0] : 4294967295 sectors at 1 (type ee)
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