[DRBD-user] moving a drbd/xen/heartbeat to another cluster

Heiko rupertt at gmail.com
Wed Feb 18 16:32:22 CET 2009


On Tue, Feb 17, 2009 at 10:34 AM, Lars Ellenberg
<lars.ellenberg at linbit.com> wrote:
> On Tue, Feb 17, 2009 at 09:48:45AM +0100, Heiko wrote:
>> On Mon, Feb 16, 2009 at 8:30 PM, Lars Ellenberg
>> <lars.ellenberg at linbit.com> wrote:
>> > On Mon, Feb 16, 2009 at 01:19:26PM +0100, Heiko wrote:
>> >> On Mon, Feb 16, 2009 at 10:58 AM, Heiko <rupertt at gmail.com> wrote:
>> >> > Hello,
>> >> >
>> >> > we have one XEN VM that is running on a lvm device, replicated with
>> >> > drbd between 2 machines and we
>> >> > now need to move this setup to another pair of machines, What is the
>> >> > best way to do this?
>> >> > The new setup will have the same paramteter than the old one, 10GB LVM device.
>> >> >
>> >> >
>> >> I missed to give some infos,
>> >> all the hosts run on Centos 5.2, drbd ist 8.0.13-1, xen is 3.1.
>> >> Would this transfer work with  an simple dd of the drbd device?
>> >
>> > yes, but only if you quiescen it before you start the dd.
>> > downtime, obviously.
>> >
>> >> Is there a way to get nearly zero downtime by adding one of the new
>> >> server to the existing cluster,
>> >> than remove both old ones and add the second new server?
>> >> Has this be done before and how would look the complete procedure?
>> >
>> > I'd probably replace the current secondary with one of the new nodes,
>> > do a _full_ sync, then switch over, and replace the other node.
>> >
>> Hello Lars,
>>
>> i wrote down all the steps I would do to transfer the VM to the new
>> pair of machines,
>> would this work that way or do I have any wrong steps in there?
>>
>> --------start-----------
>>
>> shutdown the 'old secondary' with "drbdadm down "resource""
>>
>> remove it from the config file on the 'old secondary' server
> yes.
>
>> change the resource to the new server on the 'old primary' (will this
>> work if there is more than one drbd device?)
>
> yes.
> you replace the "old secondary" with the "new server"
> in the config on the "old primary".
> (brgs. do not call nodes with their current roles,
>  as roles will change, and then it gets horribly confusing)
>
>> Add the device to the 'new secondary' config file.
>>
>> create the new device on the 'new secondary' with:
>>
>> drbdadm create-md "resource"
>> drbdadm up "resource"
>
>I prefer "adjust".

Hello,

even when I initialize a new device i can do drbdadm adjust?
I would do that on the 'old primary' when I changed to the new secondary.


> # see what drbdsetup commands would be executed
> drbdadm -d adjust "resource"
> # do it
> drbdadm adjust "resource"
>
>> drbdadm secondary "resource"
>
> not necessary.
> it is secondary already,
> and remains secondary until made primary.
>
>> than sync it, on the 'old primary' do:
>> drbdadm -- --overwrite-data-of-peer primary "resource"
>
> not necessary, and does not even do a thing,
> because it is already Primary.
>
> and the resync should already have started anyways.
> if not, double check ips and connectivity,
> then drbdadm adjust.
>
>> when thats done, shut down the resource on the 'old primary' with
>> "drbdadm down "resource"".
>> remove it from the config file on the 'old primary'.
>
> yes.
>
>> now add the resource to the configfile on the 'new primary' server.
>> change the resource in the configfile on the 'new secondary' to
>> reflect the new primary.
>
> these are not Primary server and Secondary server.
> Primary and Secondary are _roles_.
>
> I know you know that.
> but please also get used to _think_ this way,
> or you will get confused, and confuse people you talk to.
>
> the just previously synced new server can be made primary now,
> and you can go online with resources already.
>
> you can be online with the resource while it is still primary
> on one of the old servers, then just do a switchover by hand
> to the first new server you used to replicate to.
> minimal downtime.
> you could even live-migrate, if you did that before,
> and the host systems are sufficiently similar.
>
> then disconnect from the old server,
> and connect to the other new server.
>
> it is really that easy.
>
>> when thats done, make the 'new primary' a primary on the 'new primary':
>
> wow. listen to yourself.
> see what I mean?
>
yeahh, that was even confusing when writing.


I scheduled the transfer fpr tommorow morning, hope everything works flawlessly.


thx and greetings


Heiko

> --
> : Lars Ellenberg
> : LINBIT | Your Way to High Availability
> : DRBD/HA support and consulting http://www.linbit.com
>
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