[linux-lvm] Removing disk from raid LVM

[Libor Klepáč]

Hello,
but when i use

# lvs -a | grep Vokapo
output is

lvBackupVokapo                               vgPecDisk2 rwi-aor- 128.00g                                           
  [lvBackupVokapo_rimage_0]                    vgPecDisk2 iwi-aor-  42.67g                                           
  [lvBackupVokapo_rimage_1]                    vgPecDisk2 iwi-aor-  42.67g                                           
  [lvBackupVokapo_rimage_2]                    vgPecDisk2 iwi-aor-  42.67g                                           
  [lvBackupVokapo_rimage_3]                    vgPecDisk2 iwi-aor-  42.67g                                           
  [lvBackupVokapo_rmeta_0]                     vgPecDisk2 ewi-aor-   4.00m                                           
  [lvBackupVokapo_rmeta_1]                     vgPecDisk2 ewi-aor-   4.00m                                           
  [lvBackupVokapo_rmeta_2]                     vgPecDisk2 ewi-aor-   4.00m                                           
  [lvBackupVokapo_rmeta_3]                     vgPecDisk2 ewi-aor-   4.00m

what are these parts then?

it was created using
# lvcreate --type raid5 -i 3 -L 128G -n lvBackupVokapo vgPecDisk2
(with tools 2.02.104)
I was not sure about number of stripes


Libor


On Čt 12. března 2015 10:53:56 John Stoffel wrote:
> Libor> here it comes.
> 
> Great, this is a big help, and it shows me that you are NOT using
> RAID5 for your backup volumes.  The first clue is that you have 4 x
> 3tb disks and you only have a VG with 10.91t (terabytes) of useable
> space, with a name of 'vgPecDisk2'.
> 
> And then none of the LVs in this VG are of type RAID5, so I don't
> think you actually created them properly.  So when you lost one of the
> disks in your VG, you immediately lost any LVs which had extents on
> that missing disk.  Even though you did a vgcfgrestore, that did NOT
> restore the data.
> 
> You really need to redo this entirely.  What you WANT to do is this:
> 
> 0. copy all the remaining good backups elsewhere.  You want to empty
>    all of the disks in the existing vgPecDisk2 VG.
> 
> 1. setup an MD RAID5 using the four big disks.
> 
>    mdadm --create -l 5 -n 4 --name vgPecDisk2 /dev/sda /dev/sdb /dev/sdd
> /dev/sdg
> 
> 2. Create the PV on there
> 
>    pvcreate /dev/md/vgPecDisk2
> 
> 3. Create a new VG ontop of the RAID5 array.
> 
>    vgcreate vgPecDisk2 /dev/md/vgPecDisk2
> 
> 3. NOW you create your LVs on top of this
> 
>    lvcreate ....
> 
> 
> The problem you have is that none of your LVs was ever created with
> RAID5.  If you want to do a test, try this:
> 
>   lvcreate -n test-raid5 --type raid5 --size 5g --stripes 4 vgPecDisk2
> 
> and if it works (which it probably will on your system, assuming your
> LVM tools have support for RAID5 in the first please, you can then
> look at the output of the 'lvdisplay test-raid5' command to see how
> many devices and stripes (segments) that LV has.
> 
> None of the ones you show have this.  For example, your lvBackupVokapo
> only shows 1 segment.  Without multiple segments, and RAID, you can't
> survive any sort of failure in your setup.
> 
> This is why I personally only ever put LVs ontop of RAID devices if I
> have important data.
> 
> Does this help you understand what went wrong here?
> 
> John
> 
> 
> Libor> I think i have all PV not on top of raw partitions. System is on
> mdraid and backup PVs are Libor> directly on disks, without partitions.
> 
> Libor> I think that LVs:
> 
> Libor> lvAmandaDaily01old
> 
> Libor> lvBackupPc
> 
> Libor> lvBackupRsync
> 
> Libor> are old damaged LVs, i left for experimenting on.
> 
> Libor> These LVs are some broken parts of old raid?
> 
> Libor> lvAmandaDailyAuS01_rimage_2_extracted
> 
> Libor> lvAmandaDailyAuS01_rmeta_2_extracted
> 
> Libor> LV lvAmandaDailyBlS01 is also from before crash, but i didn't try to
> repair it (i think)
> 
> Libor> Libor
> 
> Libor> ---------------
> 
> Libor> cat /proc/mdstat (mdraid used only for OS)
> 
> Libor> Personalities : [raid1] [raid10] [raid6] [raid5] [raid4]
> 
> Libor> md1 : active raid1 sde3[0] sdf3[1]
> 
> Libor> 487504704 blocks super 1.2 [2/2] [UU]
> 
> Libor> bitmap: 1/4 pages [4KB], 65536KB chunk
> 
> Libor> md0 : active raid1 sde2[0] sdf2[1]
> 
> Libor> 249664 blocks super 1.2 [2/2] [UU]
> 
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