Il 06/09/11 07:59, GiBu GeorGe ha scritto:
Hai...
My primary language is not english so i am having difficluty in
understanding Persistent image concept..
What i am trying to do is port my existing servers to opennebula.. But
i want those vm to act as virtual machine normally would... Means if
any changes made to it wont disappear if the server
restart(physical/logical).. Does making it persisatant help with that
option... Or i am getting it all wrong here..
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When you restart a VM (with restart command) you don't loose anything.
The same using for example onevm xxx stop.
At the moment there isn't an OpenNebula command to phisically restart a
VM (like unplug/plug the cable in a physical server) and you have to do
this in hypervisor (for example in xen with xm destroy xxx/xm create
xxx): with this operation you don't loose anything.
When you shutdown a VM in OpenNebula you delete disks that are not
persistent (and then it's correct: persistent images are disk that
survive when you shutdown a VM in OpenNebula), but this operation is
like a deletion of a VM, not a simple restart!
The phylosophy on a cloud is a little different than a simple
virtualization system like VMWare: is to have non persistent "golden"
disk images with only S.O. and minimal configuration that can be cloned
to reach the maximum speed when you create a new VM; think this disk
like a read only disk. Then, in case, there is a second persistent disk
with persistent data.
For example you can create a VM with a distro like FreeNAS in the non
persistent disk that export via NFS a persistent volume with you web
server pages.
Then ther is a second VM with only a webserver configured that read the
web pages from FreeNAS. When you you reach the maximum load on this VM,
you can create a second webserver in a couple of seconds to scale your
application.
Bye,
Alberto
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