Hello List,
I don't get it!
I have a xen system that has a DomU of FC11 with a 20GB LV for the
disk. I created a snapshot using this command:
lvcreate -L +10G -s -n s_cgate-be1 /dev/xenvg/cgate-be1
This is the output of an 'lvdisplay' of the snapshot LV:
lvdisplay /dev/xenvg/s_cgate-be1
--- Logical volume ---
LV Name /dev/xenvg/s_cgate-be1
VG Name xenvg
LV UUID 7c1kEs-xYoO-Qxem-2E2M-hlee-pc4Q-zm6TZ5
LV Write Access read/write
LV snapshot status active destination for /dev/xenvg/cgate-be1
LV Status available
# open 2
LV Size 20.00 GB
Current LE 5120
COW-table size 10.00 GB
COW-table LE 2560
Allocated to snapshot 0.11%
Snapshot chunk size 4.00 KB
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 253:15
I then shutdown the DomU and pointed the 'Disk...' line in the config
file for the DomU to the snapshot. It boots.
OK, I must be missing the simple answer because I cannot seem to grasp
the concept of snapshots.
1. How can I have a 20GB LV as a disk and the snapshot be 10GB and
boot the entire OS?
2. Can I create a DomU and then snapshot the LV and use the snapshot
to create other DomU's?
3. If 2 is yes, would I want to continue using the snapshot as the
disk or is there something else that should be done, i.e. dd the drive
to a new LV?
In the 'lvdisplay' of the snapshot I have these extra lines:
LV snapshot status active destination for /dev/xenvg/cgate-be1
# open 2
COW-table size 10.00 GB
COW-table LE 2560
Allocated to snapshot 0.11%
Snapshot chunk size 4.00 KB
4. Does the 0.11% mean that the 10GB snapshot file is only using .11%
of the 10GB LV?
If there is a good doc out there explaining all of this could someone
just post a link. I don't mind reading but am not getting the answers
to the above. I have found lots of docs explaining how to do it but
nothing going much further than that.
Thanks for any help,
Jon
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