[Xen-users] DomU freezes after migration

[Sauro Saltini <saltini@xxxxxx>]

 Hi everybody, I'm facing a strange issue with my current setup.

I've got a working Xen 3.4.3 / DRBD 8.3.7 cluster which runs fine and is 
very stable.
I'm using for both Dom0 and DomU's a xen patched kernel 2.6.32.13 (tried 
also with 2.6.32.25 and latest gentoo ported patchset)
Since I don't need automatic failover or load balancing of guests, I've 
left out the whole Pacemaker / OpenAIS thing (installed and tested, but 
I really don't need the functionality) so I start/stop/migrate my few 
guests by hand when I need it, using simply "xm" from the commandline.
Now, the problem arises triyng to migrate a PV guest DomU.
The migration itself completes with no errors, but the migrated guest 
runs on the destination host for 20-30 seconds and then completely 
freezes - no input from keyboard, no output to console, no network 
connectivity.
If I try to shutdown the freezed DomU with "xm shutdown" nothing happens.

Now, if I migrate back the domU to the original host, I can interact 
again with it, networking works: the guest unfreezes completely.
The problem seems like the one mentioned in this thread :
http://lists.xensource.com/archives/html/xen-devel/2010-10/msg01261.html

But I've already tried to apply te mentioned patch to the DomU kernel 
without any results.
Having my domU's on drbd backed resources I've also tried to switch on 
"allow-two-primaries" in drbd.conf and do a "live migration" of the 
DomU: this way the migration works (no freeze on the destination host)
Strangest thing is that with "allow-two-primaries" I can also do "xm 
migrate" without "--live" option and again all works.
I don't want/need to allow two primaries in drbd, as the only kind of 
migration I'll want to do is "non live" and allowing dual primary poses 
some serious integrity risks on the underlying filesystems (which are 
standard reiserfs) in case of mistake.
Any clues ?

Many thanks in advance

Sauro.


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