[Gllug] Removing LVM (RHEL4)

[Rich Walker]

Bruce Richardson <itsbruce at uklinux.net> writes:

>
> LVM really does not add much complexity and actually makes maintenance
> considerably easier if you use it properly.

Well, until it gets confused.

I have /dev/md1 built up like this:

md0 : active raid1 hda1[0]
      19583168 blocks [2/1] [U_]
      
md1 : active raid5 hdf2[0] hdk2[2] hdi2[3] hdg2[4] hde2[1]
      638904576 blocks level 5, 32k chunk, algorithm 2 [5/5] [UUUUU]

I then use md1 as a pv:


thoth:~# pvdisplay 
  /dev/hdg2: lseek 4611824548433201152 failed: Invalid argument
  /dev/hdg2: lseek 4611824548433201152 failed: Invalid argument
  /dev/hdg2: lseek 4611824548433201152 failed: Invalid argument
  /dev/hdg2: lseek 4611824548433201152 failed: Invalid argument
  --- Physical volume ---
  PV Name               /dev/md1
  VG Name               bulk
  PV Size               609.30 GB / not usable 0   
  Allocatable           yes 
  PE Size (KByte)       4096
  Total PE              155982
  Free PE               14670
  Allocated PE          141312
  PV UUID               GKnn7Q-FDnz-NsYB-9Sd4-pLko-5yGH-vY6kji
   
  --- NEW Physical volume ---
  PV Name               /dev/hdg2
  VG Name               
  PV Size               510334.04 TB
  Allocatable           NO
  PE Size (KByte)       0
  Total PE              0
  Free PE               0
  Allocated PE          0
  PV UUID               ϵ¦i¾¯-C ú- §?-9 4- L  -5 GH- Y6   

Unfortunately, at some time the system has decided /dev/hdg2 is a
separate PV.

So on boot, it's a race between md and lvm as to who grabs hdg2
first. Typically, this means:

lvm hangs on to hdg2
pd assembles /dev/md1 without hdg2
lvm might or might not manage to assemble VG bulk and the corresponding
devices
booting finishes
I do mdadm --add /dev/md1 /dev/hdg2

I have tried a number of ways to remove /dev/hdg2 without breaking
/dev/md1. So far, most of them have resulted in broken arrays ...

(Backup and restore isn't an option)

cheers, Rich.


-- 
rich walker         |  Shadow Robot Company | rw at shadow.org.uk
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