[DRBD-user] drbd without a partition, for use with xen images

Heiko rupertt at gmail.com
Fri Jul 25 11:49:33 CEST 2008

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.


On Fri, Jul 25, 2008 at 11:07 AM, Robert Verspuy <robert at exa-omicron.nl> wrote:
> Michael schreef:
>>
>> Why not to use loop?
>> assing xen image to loop1 ( drbd1 (
>> loop2 to drbd2 ... etc...
>>
Hello,

do you mean that I create a Xen Image, than do a "losetup /dev/loop1
/VM/my.image"
and than configure that loop1 as a disk:

on server1 {
    device     /dev/drbd0;
    disk       /dev/loop1
    address    192.168.2.1:7788;
    meta-disk  internal;
  }

or can I just do:

on server1 {
    device     /dev/drbd0;
    disk       /VM/my.image
    address    192.168.2.1:7788;
    meta-disk  internal;
  }


>
> But then (I think), you can't do a live migration ??
> because there's no software making sure that writes to the image from both
> server do not write to the same block at the same time. (GFS does that)
>
> If you don't need live migration, you can use the loop, but when you want to
> migrate (in a controlled manner, not failover), you have to do the following
> steps:
> - On Server A, stop Xen DomU
> - On Server A, umount loop1 (drbd1)
> - On Server A, set drbd1 from primary to secundairy
> - On Server B, set drbd1 from secundairy to primary
> - On Server B, mount loop1 (drbd1)
> - On Server B, Start Xen VM.
>
we dont use live migration, for now.
We just need a failover of the 1. VM goes offline we need the other
one, with actuall data

I cant use a real partition because we have some VM on that machine
that dont need drbd replication,
also some are alone and others just do a mysql replication(inside the VM).

cheers

.rupertt

> Regards,
> Robert
>
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