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mpalmer / lvmsync

Synchronise LVM LVs across a network by sending only snapshotted changes
http://theshed.hezmatt.org/lvmsync
GNU General Public License v3.0
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Question and possible error in doc #11

Closed bussnet closed 10 years ago

bussnet commented 11 years ago

First, a very cool tool... exacly what I'm searching for ;)

I have a question.. Is it possible to transfer more than one snapshot, to reduce the downtime for frequent systems (large snapshots to transfer in the downtime)?

I mean:

  1. make snapshot
  2. transfer the snapshot
  3. make 2. snapshot
  4. lvmsync the 1. snapshot
  5. shutdown VM
  6. lvmsyn 2. Snapshot
  7. start VM

Hope you understand.

Thanks in advance.

regards, thorsten

PS: I think there is an error in the example in readme.md (should be snapshot name, not lv name)

dd if=/dev/vmsrv1/somevm-lvmscan bs=1M | pv -ptrb | ssh root@vmsrv2 dd of=/dev/vmsrv2/somevm

instead of

dd if=/dev/vmsrv1/somevm bs=1M | pv -ptrb | ssh root@vmsrv2 dd of=/dev/vmsrv2/somevm
mpalmer commented 10 years ago

Yes, you can certainly "chain" snapshots together if you need to get the delta transfer time lower, although there is of course a diminishing return as your transfers get quicker and quicker. As far as which LV to use for the initial dd, it doesn't matter, because any changes in the origin volume will get copied again during the lvmsync run anyway.