[Xen-users] Re: Xen, LVM, DRBD, Linux-HA

[Aleksandar Ivanisevic <aleksandar@xxxxxxxxxxxxx>]

Rainer Sokoll <rainer@xxxxxxxxxx> writes:

> Hi,
>
> I want to put it all together.
> So far, I have a running machine with multiple domUs, and I am very
> excited. But now I want to go a step ahead:
> I have two identical machines with a big amount of RAM and disk space.
> My goal is to hve all the domUs almost redundant - and want to ask you
> for your advice.
> The plan is to have every VM in its own logical volume and have DRBD
> replicate this volume to the other machine. Assumed Linux with Linux-HA
> runs in a VM, here comes my question:
> If the complete Linux VM runs in its own logical volume, Linux-HA cannot
> work, since the configuration must not be the same on both sides. One
> solution would be to have a minor file based backend that holds /etc/,
> /proc/, /var/, /boot/ (and maybe more?). Or maybe there is a more
> sophisticated solution?
> How would you start?

I don't really understand what exactly do you want to make redundant?

We have similar setup to yours, both cluster nodes simply have DRBD
devices in LVs for ease of administration and inside we have regular
disk images.

we sync the domU config files and the rest of the junk between nodes
using csync2.

before you undertake this adventure, be aware that xen is currently
not mature enough for such a setup, we had machines (both domUs and
dom0s) crashing regularly when having drbd in primary/primary and drbd
in primary/secondary simply does not work without heavy patching,
which is simply not worth the trouble.

right now we settled with quasi-migration, we save the domU, rsync the
memory file over to the other machine, change drbd setup to primary
and restore the machine and that more or less works ok with cca 10s
downtime.

if you only want your domUs to come up on the other node if a node
goes down, this might not be an issue though. We wanted to be able to
migrate domUs between the nodes to balance the load.

-- 
To sto si frustriran, zavidan tko zna na cemu i sto ne vidis dalje od
svoje guzice je tuzno. Da onda barem imas toliko samokontrole da
sutis umjesto da pravis budalu od sebe... izgleda da si prestar da se
promjenis na bolje. - Davor Pasaric, hr.comp.mac


_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-users