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Old 10-17-2013, 11:18 PM   #1
Registered: Oct 2003
Location: Izmir, Turkey
Distribution: Fedora Core 10
Posts: 68

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Exclamation RAID1: Urgent.. Two disks out of sync... how to get them back in sync?

Hello. I have a very simple RAID1 system.
Two identical disks sda and sdb, identical partitions on both.

The raid apparently degraded some time ago, and the system kept using /dev/sdb only.

After an fsck, the system booted from /dev/sda..
So, the system went back in time by several months!

I rescued /dev/sdb.. How can I copy stuff from each /dev/sdb partition to /dev/sda?

My intention is to boot from flash, and do a cp -pR from each /dev/sdb partition to its equivalent /dev/sda partition.

Once I collect as much data as possible, I intend to remove sdb to replace it with another drive.

Does that sound good?

Thanks, -turgut

Last edited by tkalfaoglu; 10-17-2013 at 11:46 PM.
Old 10-18-2013, 03:42 AM   #2
Registered: Apr 2009
Location: Oz
Distribution: slackware64-14.0
Posts: 875

Rep: Reputation: 282Reputation: 282Reputation: 282
You don't want to copy files as that wont fix the RAID flags.

Option 1 both drives in the same place but you can boot sdb
1. You need to boot the system from /dev/sdb
2. You need to check that your running a degraded RAID with only /dev/sdb working
3. You then add /dev/sda back with mdadm --re-add

Option 2 swap the drives so the sdb is sda and boots from there
Similar to option 1 but you swap sda for sdb

re-sync should then be in progress and you can get an indication of the time to completion from /proc/mdstat


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