Page 1 of 1

mirrored LVMs, mirror log lost and now?

Posted: 2018/07/09 20:36:50
by dah_lala
Hi all,
Some time ago I configured a mirrored volume group of two physical volumes. When I configured this I had to define another volume for the mirror log. When I did this I was already wondering what would happen to my RAID1 configuration if the drive with the mirror log fails, but I was sure that there must be a way to define another mlog or get the data from the two mirrored volumes. The original mlog was located on a partition on the system drive.

Now I had to transfer the two mirrored physical volumes/hard drives to another machine and I am unable to mount the volume group without the corresponding mlog partition. If I take the system disc (containing the mlog partition) out of the old server and put it together with the two mirrored disks in the same machine, I can mount the volume. However, it is no option to transfer the system disk of the old server to the new machine. And how can I get my data back if the mlog is lost?

Isn't there a way to create mirrored volumes without an extra partition for the mlog? mdadm also doesn't require an extra partition for a mirror log.
How should I set up such a mirror log in a better way? If it is so essential, it should be redundant as well....

Code: Select all

[root@device user]# lvs -a -o +devices  
  WARNING: Device for PV TgCMKE-dwMs-l40L-BTPm-eboW-Rbza-FoDTce not found or rejected by a filter.
  LV                 VG               Attr       LSize    Pool Origin Data%  Meta%  Move Log            Cpy%Sync Convert Devices                                
...               
  lv_raid            vg_mirror        mwi---m-p- <931.51g                                [lv_raid_mlog]                  lv_raid_mimage_0(0),lv_raid_mimage_1(0)
  [lv_raid_mimage_0] vg_mirror        Iwi---m--- <931.51g                                                                /dev/sdb1(0)                           
  [lv_raid_mimage_1] vg_mirror        Iwi---m--- <931.51g                                                                /dev/sdd1(0)                           
  [lv_raid_mlog]     vg_mirror        lwi---m-p-    4.00m                                                                [unknown](0)                           
...
Thanks a lot!