mdadm - Recovering a 'split' RAID1 array

Posted by Hamza on Server Fault See other posts from Server Fault or by Hamza
Published on 2012-11-04T15:57:19Z Indexed on 2012/11/04 17:03 UTC
Read the original article Hit count: 262

Filed under:

linux

|

raid

|

mdadm

I have two drives that used to be part of a single RAID1 volume but it appears that one of them went offline for some time, something I've noticed just now when I rebooted my system.

I now seem to have two RAID volumes, as reported by:

# cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] 
md126 : active raid1 sdc[1]
      2096116 blocks super 1.2 [2/1] [_U]

md127 : active (auto-read-only) raid1 sdb[0]
      2096116 blocks super 1.2 [2/1] [U_]

unused devices: <none>

Not exactly sure where to go from here. How can I merge and re-sync these volumes without data loss?

Thanks.

© Server Fault or respective owner

Related posts about linux

apt-get install and update fail

as seen on Ask Ubuntu - Search for 'Ask Ubuntu'
I've got a problem with apt-get update and apt-get install ... commands . every time update or installing fails and errors are : Get:1 http://dl.google.com stable Release.gpg [198B] Ign http://dl.google.com/linux/chrome/deb/ stable/main Translation-en_US Get:2 http://dl… >>> More
kernel module compiling error

as seen on Ask Ubuntu - Search for 'Ask Ubuntu'
sh@ubuntu:/home/ccpp/helloworld$ make gcc-4.6 -O2 -DMODULE -D_KERNEL_ -W -Wall -Wstrict-prototypes -Wmissing-prototypes -isystem /lib/modules/`uname -r`/build/include -c -o hello-1.o hello-1.c hello-1.c:4:0: warning: "MODULE" redefined [enabled by default] <command-line>:0:0: note: this is… >>> More
Build-Essentials installation failing

as seen on Ask Ubuntu - Search for 'Ask Ubuntu'
I am having trouble accessing the several critical header files that show to be a part of the build process. The "Ubuntu Software Center" shows "Build Essentials" as installed: Next I did the following two commands, which did not improve the problem: ~$ sudo apt-get install build-essential [sudo]… >>> More
Updating Debian kernel

as seen on Super User - Search for 'Super User'
I'm trying to update my Debian machine to 2.6.32-46 (which is the new stable). However, after doing apt-get update my apt-cache search linux-image shows me: linux-headers-2.6.32-5-486 - Header files for Linux 2.6.32-5-486 linux-headers-2.6.32-5-686-bigmem - Header files for Linux 2.6.32-5-686-bigmem linux-headers-2… >>> More
Serial connection over a single USB cable (Windows to linux, or linux to linux)

as seen on Server Fault - Search for 'Server Fault'
I'm helping out with a project for an embedded device that only has USB and no serial. This device is running Linux. These days, when we need to connect to a serial port on a device we typically use a USB to serial adapter (on something like a phone system or a load balancing device, etc). I would… >>> More

Related posts about raid

Booting from integrated RAID controller when another RAID controller is installed in a PCIe slot

as seen on Server Fault - Search for 'Server Fault'
I have a GA MA785GT UD3H motherboard with Windows Server 2008 R2 installed on a RAID1 using the on-board RAID controller. I have now installed a RocketRaid 2680 controller and set up a RAID5 for all my data to be stored on. Unfortunately I now cannot boot from the RAID1 anymore, the PC is trying… >>> More
Onboard RAID vs Software RAID

as seen on Server Fault - Search for 'Server Fault'
My motherboard, an Asus M4a79t Deluxe, advertises RAID 0/1/5 capabilities. My limited understanding is that onboard RAID is better than software RAID. Is this necessarily true? Is an onboard RAID controller closer in performance to a software controller or a dedicated hardware controller? >>> More
RAID-1 and regular drive removal (using RAID-1 as a backup measure)

as seen on Super User - Search for 'Super User'
Is using mdadm's RAID-1 of 2 partitions (one on laptop's internal HDD, one on external HDD) a good idea. I want the system to work as RAID-1 if both drives are present, work as regular volume (degradad RAID-1) if external HDD is unplugged and quickly resync when I plug external HDD again. Questions: Is… >>> More
Explain difference in SQLIO numbers for RAID 0 versus RAID 5 over 6 disks

as seen on Stack Overflow - Search for 'Stack Overflow'
When using the SQLIO benchmark tool on a 4-core Dell server with 6 15k 450GB (fast) drives, RAID 0, we found the max throughput was 2MB per second. But when configured as RAID 5, we get 30 MB per second. It seems that the RAID controller, Dell Perc 5i integrated controller, is maxing out the… >>> More
RAID 5 RECONSTRUCT with RAID Reconstructor

as seen on Server Fault - Search for 'Server Fault'
I have Dell Poweredge server 2600 with Raid 5 in 3 hard drive Scsi 36gb each, it was fail to boot sinc the third drive is offline. I attached Sata card adapter to Sata hard drive and install OS SERVER 2003 to it, downloaded drivers for Raid and everything goes fine when I use recovery data software… >>> More