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Old 01-18-2015, 09:54 AM   #1
Registered: Apr 2013
Distribution: RedHat, Cent, Ubuntu
Posts: 80

Rep: Reputation: Disabled
Get RAID1 and LVM back after re installating the OS

Hi All,
I had installed Cent OS 6.6 on sda. The RAID1 and LVM setup was on sdb and sdc. To practice well on recovering RAID and LVM after the OS reinstallation, I just reinstalled the OS. During first re installation of OS, I had selected all the mount points including RAID/LVM partitions as same as how those where mounted before the reinstallation, but the format was selected to only /, /others, /var. And after booting /dev/md0 and LVM partitions were set to active automatically and everything was mounted properly. Also there was no any data loss in the RAID/LVM partitions. So I could made sure that everything will be perfect if we carefully select the mount points during OS reinstallation by making sure the formating partitions.

Now I thouht of reinstalling OS once again but this time didn't select mount points for RAID/LVM partitions during OS reinstallation, thought for manual setup after the installation. So just selected /, /others, /var partitions to format. When it booted, I ran "cat /proc/mdstat" but it was taken /dev/md127(read only) instead of /dev/md0.
# cat /proc/mdstat 
Personalities : [raid1] 
md127 : active (auto-read-only) raid1 sdc[1] sdb[0]
      52396032 blocks super 1.2 [2/2] [UU]
unused devices: <none>
So now I just wanted to stop and restart this RAID array as /dev/md0. But I am not able to stop as it is giving following error.
# mdadm --stop --force /dev/md127
mdadm: Cannot get exclusive access to /dev/md127:Perhaps a running process, mounted filesystem or active volume group?
I made sure that no one RAID/LVM partitions are mounted.
# df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/sda1        15G  3.5G   11G  26% /
tmpfs           376M     0  376M   0% /dev/shm
/dev/sda2       4.7G  9.8M  4.5G   1% /others
/dev/sda3       2.9G  133M  2.6G   5% /var
But LVM is active
# pvdisplay 
  --- Physical volume ---
  PV Name               /dev/md127
  VG Name               data
  PV Size               49.97 GiB / not usable 4.00 MiB
  Allocatable           yes 
  PE Size               4.00 MiB
  Total PE              12791
  Free PE               5111
  Allocated PE          7680
  PV UUID               IJ2br8-SWHW-cf1d-89Fr-EEw9-IJME-1BpfSj
# vgdisplay 
  --- Volume group ---
  VG Name               data
  System ID             
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  19
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                2
  Open LV               0
  Max PV                0
  Cur PV                1
  Act PV                1
  VG Size               49.96 GiB
  PE Size               4.00 MiB
  Total PE              12791
  Alloc PE / Size       7680 / 30.00 GiB
  Free  PE / Size       5111 / 19.96 GiB
  VG UUID               982ay8-ljWY-kiPB-JY7F-pIu2-87uN-iplPEQ
# lvdisplay 
  --- Logical volume ---
  LV Path                /dev/data/home
  LV Name                home
  VG Name                data
  LV UUID                OAQp25-Q1TH-rekd-b3n2-mOkC-Zgyt-3fX2If
  LV Write Access        read/write
  LV Status              available
  # open                 0
  LV Size                10.00 GiB
  Current LE             2560
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           253:0
  --- Logical volume ---
  LV Path                /dev/data/backup
  LV Name                backup
  VG Name                data
  LV UUID                Uq6rhX-AvPN-GaNe-zevB-k3iB-Uz0m-TssjCg
  LV Write Access        read/write
  LV Status              available
  # open                 0
  LV Size                20.00 GiB
  Current LE             5120
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           253:1
As LVM is active on /dev/md127 it is not allowing to stop /dev/md127 raid array. So as I am fresher in RAID/LVM, expecting your kind help to make LVM inactive without any data loss and restart the RAID array as /dev/md0 and then re activate the LVM setup.
Expecting your kind reply, Thanks.

Last edited by cli; 01-18-2015 at 11:08 AM.
Old 01-18-2015, 08:33 PM   #2
Registered: Apr 2013
Distribution: RedHat, Cent, Ubuntu
Posts: 80

Original Poster
Rep: Reputation: Disabled
Dear Members/Guru, may I get your kind help for the same?


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