[PVE-User] taking advantage of the lvm snapshot

Tonči Stipičević tonci at suma-informatika.hr
Sat Jul 7 00:05:43 CEST 2012

Hello to all,

I'm running pve2.1 cluster with shared lvm2 storage (nexenta) and am 
very satisfied so far .

scheduled (and manual)  backups are working very good and backup files 
are copied to another shared nfs storage.

So when we have to return to the backup first we have to restore the 
archive what could last depending on the amount of data .
2nd.. every backup takes time .. but when we make backup of the VM that 
are on the lvm volumes then 1st step is snapshoting the logical VMID 
volume  which makes very useful quasi-backup of the VM.
We are using it to make archive of the VM in the same time the original 
VM is running which makes zero-downtime .. which is also very very good.

But using this backed-up VM again means restoring it again which also 
takes time.

So my question would be whether this snapshot (i.e. 101-s) could be used 
to make copy (delta-replica) to  another-equivalent logical volume (i.e. 
201 ) on the second storage   so that this 201-VM is ready to run 
without restoring the archive. So VM201 will always be down so that 
logvolume cannot be locked ... (Am I right?)

I hope dd could do that job but dd cannot transfer only changed blocks 
next time copying is done ?  or it can ?

So my idea would be to make fast cloning of VMs on the another storage 
that are usable right away !   is there any scenario to achieve this ?

This could be something called offline-VM-cloning (for me it is not 
necessary to achieve drbd features )

Since we had snapshot that is done in moment it would very useful if we 
could transfer only changes over to the 201 volume  ( after the initial 
full replication )

Thank you very much in advance for your attention
and help

srdačan pozdrav / best regards

Tonči Stipičević, dipl. ing. elektr.

SUMA Informatika d.o.o.
Badalićeva 27 10000 Zagreb
fax: 01 5560007
mob: 091 1234003

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