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Old 04-20-2011, 08:13 PM   #1
jtag
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software raid (mirror); mount partition


I have a Ubuntu linux software raid (mirror) md0 of sda1 and sdb1. My sda1 is bad. How can I mount only sdb1? I cant mount sdb1 since initially was declared as raid and not as ext3.
 
Old 04-20-2011, 09:31 PM   #2
jason_not
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Hello,

Have a look at the mdadm man page, in the "Manage" section. Something like:

mdadm /dev/md0 --fail /dev/sda1 --remove /dev/sda1

After this, you should (I think) be able to mount /dev/md0 if you need to.

once you replace the device, (or if you have another disk already to replace it) you should be able to run
mdadm /dev/md0 --add /dev/<devicename>

Hope this helps...

--jason
 
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Old 04-22-2011, 07:21 PM   #3
jtag
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I stooped sdb4 from array using graphical interface "Disk Utility". Then:

sudo mkdir /mnt/sdb4
sudo mount /dev/sdb4 /mnt/sdb4
mount: unknown filesystem type 'linux_raid_member'

----------

sudo mount /dev/md1 /mnt/sdb4
mount: you must specify the filesystem type
 
Old 04-23-2011, 12:26 AM   #4
jason_not
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Hi There,

I am not sure how /dev/sdb4 came about, or /dev/md1. Did you mean /dev/sdb1 as in your original post? I will assume such...

Look at the contents of /proc/mdstat. The file will show every /dev/md* array, and the partitions that make them up. On your system, I would expect to see something showing /dev/md0 as being active raid1, and composed of sdb1 and sda1. If you don't see any md* devices listed, or there is no /proc/mdstat file, maybe your system hasn't loaded the appropriate module.

You will not be able to directly mount a partition that was once part of an array. You must remove the bad partition from the array, then mount the array again. You can't remove the good partition and expect to mount it separately from the array. When you get the error unknown filesytem type "linux raid member", that actually is what the partition manager is saying about the partition signature. This partition is only accessible through the software raid manager.

If I go back to your original post, and my original answer, once you break the bad /dev/sda1 partition away from the array, you should still be able to mount /dev/md0 with only the one partition in it. It will be mounted in degraded mode, but it should be there. Fortunately, you can do that since you used mirroring.

I have never used the gui disk utility tool, so I don't know how well it runs. Most gui tools though don't fully implement all disk tools: that's why I have only used the command line tools.

For more details, please look at the following page: http://tldp.org/HOWTO/Software-RAID-HOWTO.html
 
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Old 05-08-2011, 07:09 PM   #5
jtag
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Worked,
I removed the raid from graphical interface (then the file /proc/mdstat was almost empty); then I mounted "sudo mount -t ext4 /dev/sdb4 /mnt/sdb4/" (sorry initially I mentioned sdb1; however)
 
  


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