[PVE-User] WG: WG: DRBD+ Proxmox2.1 + Debian Squeeze

[Holger Ernst]

> Betreff: Re: [PVE-User] WG: DRBD+ Proxmox2.1 + Debian Squeeze
> 
> > Then you have to be aware that starting a snapshot of a running
system
> > is like switching a running machine off and on again.
> > So make sure the os can handle that.
> 
> Thanks for sharing. but what if i use DRBD isnt it like switching
> machine off and on when my primary base machine goes down ?

[|] That is right. Even using proxmox backup in snapshot mode will
produce such a situation. This is happening always if you copy a running
system without a methode to copy and restore memory content and cpu
state.
So propper method would be shutdown/copy/start - but this results in
serious down-time.
So you chose between no downtime and eventually corrupted machine and
lot of downtime and no corruption in any way.
But luckily most of the time the os'es are robust enough...

> 
> as per my very limited knowlege. DRBD is also kind of a mirror b/w two
> computer or Raid 1.  in Rsync the problem is that i have to do it
> manually every hour and in DRBD the changes are updated instantly.

[|] That is correct but if you use DRBD in sync mode (that is what you
should do) disk io is limited to the connection speed between the two
syncing nodes. So in some scenarios it is not applicable.
> 
> please correct me if i understand some thing wrong .......
> 
regards, Holger