[linux-lvm] Can't make an on-line snapshot with LVM !

[armani]

Dear Sir

I don't know that if this is a FAQ.
But when I create a snapshot for my LV2

# lvcreate -L1M -s -nsnapshot1 /dev/VG1/LV2
lvcreate -- rounding size up to physical extent boundary
lvcreate -- WARNING: the snapshot will be automatically disabled once it
gets full
lvcreate -- INFO: using default snapshot chunk size of 64 KB for
"/dev/VG1/snapshot1"
lvcreate -- doing automatic backup of "VG1"
lvcreate -- logical volume "/dev/VG1/snapshot1" successfully created

This will create a /dev/VG1/snapshot1 for me.

But I can't mount it with the following command:
# mount /dev/VG1/snapshot1 /mnt
when I still mount  /dev/VG1/LV2 on my /var1 mount point.

After umount /var1
# umount /var1

Then redo the command
# lvcreate -L1M -s -nsnapshot2 /dev/VG1/LV2

This will be ok ..

What's wrong with the snapshot ?