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what happens after removing a lun from lvm under linux

Posted on 2010-08-29
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Last Modified: 2012-06-21
Hi:

     We have been undergoing some disk problems on a type 6 raid.
     We have 4 luns and want to move the data to another lun. Then remove
     the problematic lun.
     This is run under Centos 5.3 and the 4 luns are grouped together by lvm.
     We added lun5 and put it under the lvm so linux now sees
     5 devices /dev/dm-0 through /dev/dm-4. I added /dev/dm-4 to the volume group.
    And am currently running pvmove. to move the extents from the problematic pv. (dm-1).

   The question is after I remove dm-1 from the volume group and then remove the lun
   will I have problems recognizing my data.

   The reason I ask is that normally linux may see the following disks:
  /dev/sda, /dev/sdb. /dev/sdc. When /dev/sdb is removed /dev/sdc will become
  /dev/sdb on a rescan. So I was wondering if I will see the same problems here.

  I have
    1 - luns, 2 - multipath mapping, and 3 - lvm.

  Thank you for your help.
   
           
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Question by:kot_linuxoid
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Accepted Solution

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jmslagle earned 500 total points
ID: 33558520
If you are using LVM, then LVM will figure out the disk identities by metadata stored on disk, not the device name.  Additionally, it's usually wise to tell your FSTAB to mount by uuid or label for the same reason.
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Author Comment

by:kot_linuxoid
ID: 33564617
thank  you very much.
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Author Closing Comment

by:kot_linuxoid
ID: 33564639
He answered my concerns, and I knew that the
multipath drivers depend on a wwid to map.
So I didn't need info on the multipath. But to have been complete referring to the multipath(s) should
have been discussed as well.

In either case thanks to imslagle for his answer.
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