[linux-lvm] Interesting LVM1 to LVM2 migration issues.

[Jake Roersma]

I ran into an interesting problem after I upgraded from LVM1 to LVM2
that I would like to share.  My setup when running LVM1 with linux
kernel 2.4.20 consisted of 6 logical volumes (lv_home, lv_opt, lv_use,
lv_var, lv_var_snap, lv_var_copy) all in the same volume group called
lvm00.  lv_var_snap was a test LV that I setup to snapshot lv_var, and
lv_var_copy was a seperate LV that I used to copy lv_var with, all of
which were the same size.  

After I migrated to LVM2 I found that with device mapper it was seeing
the original LV lv_var as lv_var-real, which is only the begining of my
troubles. After fixing fstab to point to the new naming of my lv_var, I
decided since I was not using lv_var_snap and lv_var_copy that I should
removed them.  After removing lv_var_snap I noticed that the device file
for lv_var-real was gone, both in /dev/mapper and in /dev/lvm00. 
Interestingly enough /var was still mounted and operational.  I ran
vgscan and vgchange -a y, and that found all of my LV's but now my
lv_var-real was renamed back to its original lv_var.  Luck for me I
noticed this and was able to update fstab before I rebooted.

My question is, why does LVM2 feel the need to change the names of the
logical volumes that I have created?  I feel perfectly confident in my
naming abilities :)..  Also, why after deleting a snapshot of an LV, was
the original LV device file (although with its new name) removed with
it?  And, after I ran vgscan and vgchange -a y, why did LVM2 feel the
need to change the name of my LV back to its original name? Thanks for
the help.

- Jake






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