[DRBD-user] no sync within VM with Xen

Adam Goryachev mailinglists at websitemanagers.com.au
Sun Aug 14 14:24:50 CEST 2016

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

On 14/08/2016 00:12, Clément Février wrote:
> Hello,
> I run into a problem. I have two node with Ubuntu, LVM2, DRBD 8.4 and
> Xen. I set up a Logical Volume with DRBD and it seems to work:
> On the primary node (named server),
> % cat /proc/drbd
> version: 8.4.5 (api:1/proto:86-101)
> srcversion: 5A4F43804B37BB28FCB1F47
>   0: cs:Connected ro:Primary/Secondary ds:UpToDate/UpToDate C r-----
>      ns:4259836 nr:8 dw:212 dr:4269307 al:4 bm:0 lo:0 pe:0 ua:0 ap:0 ep:1
> wo:f oos:0
> and on the secondary node (server2),
> % cat /proc/drbd
> version: 8.4.5 (api:1/proto:86-101)
> srcversion: D496E56BBEBA8B1339BB34A
>   0: cs:Connected ro:Secondary/Primary ds:UpToDate/UpToDate C r-----
>      ns:8 nr:4259836 dw:4259844 dr:1645 al:1 bm:0 lo:0 pe:0 ua:0 ap:0
> ep:1 wo:f oos:0
> So everything looks fine. I made an initial sync between nodes. If I
> mount the partition /deb/drbd0 on the primary node and make changes, it
> is sync properly (checked by umnounting on server, switching to
> secondary, setting primary on server2, then mounting the partition).
> This partition is actually the root of a VM. If I launch the VM, make
> some changes, stop the VM, and mounting the partition on the other node,
> then I can see that the partition is unchanged, ie in the state before
> the modifications within the VM.
> Is there a specific configuration in Xen or DRBD to make?
> What am I missing?

Make sure your VM configuration (xen config file) references the drbd 
resource and not the underlying disk. eg: use /dev/drbd0 or /dev/drbd/0 
and not /dev/sda2 or whatever...

In the meantime, since you have already modified the underlying device, 
you should do a full verify and re-sync on the DRBD device.


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