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View Full Version : [SOLVED] Cannot re-add disk to raid1 after removing with mdadm



klausmedk
September 9th, 2013, 08:57 PM
Hello
I wanted to test drive failure on my raid1 array.

My array initially looked like this:


/dev/md1p1:
Version : 1.0
Creation Time : Thu Mar 22 15:55:42 2012
Raid Level : raid1
Array Size : 2930265407 (2794.52 GiB 3000.59 GB)
Used Dev Size : unknown
Raid Devices : 2
Total Devices : 2
Persistence : Superblock is persistent

Update Time : Mon Sep 9 21:17:32 2013
State : clean
Active Devices : 2
Working Devices : 2
Failed Devices : 0
Spare Devices : 0

Name : HEV271-NAS:1
UUID : 24f6612a:f9045c3c:a09823be:0a00399b
Events : 18353

Number Major Minor RaidDevice State
0 8 32 0 active sync /dev/sdc
1 8 48 1 active sync /dev/sdd


I then set /dev/sdd faulty and removed it with:



mdadm --manage --set-faulty /dev/md1p1 /dev/sdd
mdadm /dev/md1p1 -r /dev/sdd


Then I wanted to re-add the device with:


mdadm /dev/md1p1 -a /dev/sdd

But got the response: mdadm: /dev/sdd not large enough to join array

Why is that? It's the same disk that was in the array just a second ago?

The detailts for the disks are:


sudo fdisk -l /dev/sdc

WARNING: GPT (GUID Partition Table) detected on '/dev/sdc'! The util fdisk doesn't support GPT. Use GNU Parted.


Disk /dev/sdc: 3000.6 GB, 3000592982016 bytes
255 heads, 63 sectors/track, 364801 cylinders, total 5860533168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disk identifier: 0x00000000

Device Boot Start End Blocks Id System
/dev/sdc1 1 4294967295 2147483647+ ee GPT
Partition 1 does not start on physical sector boundary.


sudo fdisk -l /dev/sdd

WARNING: GPT (GUID Partition Table) detected on '/dev/sdd'! The util fdisk doesn't support GPT. Use GNU Parted.


Disk /dev/sdd: 3000.6 GB, 3000592982016 bytes
255 heads, 63 sectors/track, 364801 cylinders, total 5860533168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disk identifier: 0x00000000

Device Boot Start End Blocks Id System
/dev/sdd1 1 4294967295 2147483647+ ee GPT
Partition 1 does not start on physical sector boundary.


What have I done wrong?
What can I do to correct my mistake without losing data?

Regards
Klaus

SaturnusDJ
September 10th, 2013, 02:33 PM
Used Dev Size : unknown

That's a bit strange.

Can you post the examine's?

klausmedk
September 10th, 2013, 02:48 PM
Thank you for the response.

mdadm examines are:


sudo mdadm --examine /dev/sdc
/dev/sdc:
Magic : a92b4efc
Version : 1.0
Feature Map : 0x0
Array UUID : 24f6612a:f9045c3c:a09823be:0a00399b
Name : HEV271-NAS:1
Creation Time : Thu Mar 22 15:55:42 2012
Raid Level : raid1
Raid Devices : 2

Avail Dev Size : 5860532896 (2794.52 GiB 3000.59 GB)
Array Size : 2930266448 (2794.52 GiB 3000.59 GB)
Super Offset : 5860533152 sectors
State : clean
Device UUID : 1f43ca76:1efe8a74:a9a477d1:0064dbe4

Update Time : Tue Sep 10 15:43:28 2013
Checksum : 75778816 - correct
Events : 18575


Device Role : Active device 0
Array State : A. ('A' == active, '.' == missing)


and


sudo mdadm --examine /dev/sdd
/dev/sdd:
MBR Magic : aa55
Partition[0] : 4294967295 sectors at 1 (type ee)


I wiped the partition table on sdd before trying to add to the array again in order to make the system belŠeive it was a completely fresh disk.
I guess that's why you see nothing for that disk.

Regards
Klaus

klausmedk
September 12th, 2013, 08:37 PM
I moved on and created a new array from scratch.
Now I use partitions instead of raw devices, and made the partitions a little smaller than the entire disk to avoid that something similar will happen again. This also mean that if I ever have to replace a disk with another one of not quite the same size it will probably fit anyway.

I used:

create partition sdd1 on orphan disk with 100 MB free space both before AND after the partition
create new array with:

sudo mdadm --create /dev/md0 --level=2 --raid-devices=2 /dev/sdd1 missing
rsync all files from old array (/dev/md1) to new array (/dev/md0)
stopped old array
created a partition sdc of similar size as sdd1
added the last disk from the old array to the new array with :

sudo mdadm --manage /dev/md0 -add /dev/sdc1