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Discussions on RAM, DRAM, shared memory, NAS, SAN, RAID, backups, SCSI, IDE, UFS, UFS2, JFS, JFS2, EXT2, EXT3
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designeru
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Post subject: Mdadm - Linux software RAID | Posted: Mon May 17, 2010 6:08 pm |
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Joined: Thu Dec 31, 2009 4:44 pm
Posts: 10
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Mdadm - Linux software RAID
I'm not going to explain what a software RAID is. There is google for this. However, i will try to summarize here how to remove a failed disk and add a new one instead of it. Follow the steps and ask if somethig failes... 1. Set the drive (in my example /dev/sda) as faulty Code: # mdadm --manage --set-faulty /dev/md0 /dev/sda 2. Remove the faulty disk from the array Code: # mdadm /dev/md0 -r /dev/sda 3. Stop the array Code: # mdadm -S /dev/md0 4. Re-assemble the RAID device Code: # mdadm --assemble --force /dev/md0 /dev/sda /dev/sdb /dev/sdc You should have something like this now (sizes and name may be different) Code: storage:~# mdadm --detail /dev/md0
/dev/md0:
Version : 00.90
Creation Time : Mon May 17 16:49:05 2010
Raid Level : raid5
Array Size : 1953524992 (1863.03 GiB 2000.41 GB)
Used Dev Size : 976762496 (931.51 GiB 1000.20 GB)
Raid Devices : 3
Total Devices : 2
Preferred Minor : 0
Persistence : Superblock is persistent
Update Time : Mon May 17 16:50:04 2010
State : clean, degraded
Active Devices : 2
Working Devices : 2
Failed Devices : 0
Spare Devices : 0
Layout : left-symmetric
Chunk Size : 32K
UUID : 4fbf11f1:d86da25c:0d590f16:adff46fb
Events : 0.2
Number Major Minor RaidDevice State
0 8 0 0 active sync /dev/sda
1 8 16 1 active sync /dev/sdb
2 0 0 2 removed
storage:~# cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md0 : active raid5 sdb[1] sda[0]
1953524992 blocks level 5, 32k chunk, algorithm 2 [3/2] [UU_] 5. Add the new good disk to the raid array Code: # mdadm /dev/md0 -a /dev/sdc
mdadm: re-added /dev/sdc You should have it like this now: Code: storage:~# mdadm --detail /dev/md0
/dev/md0:
Version : 00.90
Creation Time : Mon May 17 16:49:05 2010
Raid Level : raid5
Array Size : 1953524992 (1863.03 GiB 2000.41 GB)
Used Dev Size : 976762496 (931.51 GiB 1000.20 GB)
Raid Devices : 3
Total Devices : 3
Preferred Minor : 0
Persistence : Superblock is persistent
Update Time : Mon May 17 16:52:10 2010
State : clean, degraded, recovering
Active Devices : 2
Working Devices : 3
Failed Devices : 0
Spare Devices : 1
Layout : left-symmetric
Chunk Size : 32K
Rebuild Status : 0% complete
UUID : 4fbf11f1:d86da25c:0d590f16:adff46fb
Events : 0.6
Number Major Minor RaidDevice State
0 8 0 0 active sync /dev/sda
1 8 16 1 active sync /dev/sdb
[color=#FF0000]3 8 32 2 spare rebuilding /dev/sdc[/color]
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Darwin
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Post subject: Re: Mdadm - Linux software RAID | Posted: Mon Nov 28, 2011 3:44 am |
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Joined: Tue Nov 08, 2011 7:57 am
Posts: 3
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I have a software raid 1 with mdadm and two 1 TB disks. Today I booted and I saw the the message that the raid activated normal but with only one out of two disks. So I I got the following output form this command:
mdadm -D /dev/md0
/dev/md0:
Version : 1.2
Creation Time : Sat Apr 16 00:30:53 2011
Raid Level : raid1
Array Size : 976758841 (931.51 GiB 1000.20 GB)
Used Dev Size : 976758841 (931.51 GiB 1000.20 GB)
Raid Devices : 2
Total Devices : 1
Persistence : Superblock is persistent
Update Time : Tue Oct 18 18:33:39 2011
State : clean, degraded
Active Devices : 1
Working Devices : 1
Failed Devices : 0
Spare Devices : 0
Name : archiso:0
UUID : 96ad7277:0da83ae5:25ef36da:cb4596d3
Events : 880419
Number Major Minor RaidDevice State
0 8 17 0 active sync /dev/sdb1
1 0 0 1 removed
So I tried to re-add the disk with this command:
sudo mdadm --re-add /dev/sdc1 /dev/md0
but I got this error:
mdadm: /dev/sdc1 does not appear to be an md device
In gparted I also can see the disk and in the BIOS, too, so it's there and the disk seems to work.
Can anyone tell me what to do and I don't want to loose data and too much time and just re-add the disk. (Of course I do have backups!!)
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admin
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Post subject: Re: Mdadm - Linux software RAID | Posted: Tue Dec 06, 2011 8:32 am |
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Site Admin
Joined: Mon Aug 03, 2009 8:43 am
Posts: 95
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Try: Code: sudo mdadm /dev/md0 -a /dev/sdc1
_________________ VPSie - SSD VPS servers in AMS-IX, LINX, DE-CIX https://vpsie.com
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jacob6580
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Post subject: Re: Mdadm - Linux software RAID | Posted: Fri Feb 24, 2012 6:35 am |
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mdadm can handle anything which presents to the kernel as a block device . This can encompass whole disks (/dev/sda), partitions (/dev/sda1) and USB flash drives
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jacob6580
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Post subject: Re: Mdadm - Linux software RAID | Posted: Tue Feb 28, 2012 6:15 am |
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I tried to re-add the disk with this command:
sudo mdadm --re-add /dev/sdc1 /dev/md0
but I got this error:
mdadm: /dev/sdc1 does not appear to be an md device
In gparted I also can see the disk and in the BIOS, too, so it's there and the disk seems to work.
Can anyone tell me what to do and I don't want to loose data and too much time and just re-add the disk. (Of course I do have backups!!)
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bealee08
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Post subject: Re: Mdadm - Linux software RAID | Posted: Tue Jun 05, 2012 5:31 am |
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Joined: Fri Jun 01, 2012 9:54 am
Posts: 3
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I have been googling about software RAID and I just land to this post right on time, exactly just when I needed some of this knowledge and tutorials. Free demo's is raining in this forum and I'm liking it here.
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