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IDProjectCategoryView StatusLast Update
0005248CentOS-6lvm2public2011-11-16 14:45
Reporterppruchnerovic 
PrioritynormalSeveritymajorReproducibilityalways
Status newResolutionopen 
Platformx86_64OSCentOSOS Version6
Product Version6.0 
Target VersionFixed in Version 
Summary0005248: root on mirrored lvm failover problem
DescriptionHello,

I played with LVM mirror on SAN with success, but you have to configure also mirrored mirror log. All fail-over scenarios worked well.

I tried to configure root partition on mirrored lvm on vmware esxi 4.1 virtual machine.
I installed centos 6 on single drive and then created lvm mirror for root partition on second disk.
For boot I used mdadm raid because grub 1 can't boot from LVM.
Everything worked well till I tried to remove one of the disks. I tried to start virtual machine with only one disk, it finds boot partition but degraded LVM mirror fails to activate.
I need to use LVM mirror because it supports SSD disks, while mdadm not(at least not in centos 6). I also tried to remove one of the disks while VM was running, VM became unresponsive.
If I reconnect missing disk, VM starts normally. I also tried to modify parameters in /etc/lvm/lvm.conf so it should drop filed disk and continue to operate
mirror_log_fault_policy = "remove"
mirror_image_fault_policy = "remove"
but without success.
I guess it is a bug in LVM, because I don't see any mistake in my configuration, or maybe LVM mirror wasn't designed to work for root mount point. In change log for lvm2 ver 2.02.87-3 is:
- Fix failure to down-convert a mirror to linear due to udev "dev open" conflict.
I installed lvm2 and device-mapper packages from rhel 6.2 beta just to test it.
I got to the point where removing disk from running virtual machine resulted only in read-only filesystem, not whole system crash, but VM with missing mirrored disk still won't boot, I have to fix mirror from booted liveCD.
In last version of LVM there is added functionality "Support for MD's RAID personalities has been added to LVM." so I guess thats a way to go but it still is only a technology preview.
Steps To Reproduce - Install Centos 6 with /boot on md raid of two disks and / only on one disk.
 - convert linear / to lvm mirror
lvconvert -m1 --mirrorlog mirrored /dev/vg_root/LogVol00 /dev/sda2 /dev/sdb2 /dev/sda3 /dev/sdb3
 - same for swap
lvconvert -m1 --mirrorlog mirrored /dev/vg_root/LogVol01 /dev/sda2 /dev/sdb2 /dev/sda3 /dev/sdb3
 - try starting virtual machine without one of the disks
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Issue History

Date Modified Username Field Change
2011-11-16 14:45 ppruchnerovic New Issue