On Thu, Feb 04, 2010 at 01:40:26AM +0100, Zoran Popovi? wrote:
> I am wondering if there is a way to solve the following problem: I suppose
> that the usual way is to establish distributed file system with locking
> mechanisms like it is possible with GFS and Red Hat Cluster Suite or
> similar, but I am interested in doing some of this manually and ONLY with
> raw devices (no file system), or simply in knowing some general
> principles. The case: I have a VLUN (on FC SAN) presented on two servers,
> but mounted only on one host - to be more precise, used by a Xen HVM guest
> system as a raw physical phy:// drive. Then, I put this guest down, and
> bring it manually up on second host - it can see changed images, and make
> changes to the presented disks. Then I put it down there, and bring it up
> again on the first host - BUT THEN, this guest (or host) doesn't see
> changes made by the second system, it still sees the picture as it was the
> way it left it.
> Or even better, if I bring HVM guest on a host, then put it down, make
> restore of his disks on the storage (I am using HP EVA8400, restoring
> original disk from a snapshot - it does have redundant controllers but
> their cache must be in sync for sure), and then bring it up - it still
> sees things on the disks as they were before restore. But if I _RESTART_
> the host, it can see restored disks correctly. Now, I am wondering why is
> this happening, and if it is possible somehow to resync with the storage
> without restart (I wouldn't like that on production ! and on our windows
> systems this is possible) ... I've tried sync (but that is like flushing
> buffer cache), and I didn't try echo 3 > /proc/sys/vm/drop_caches after
> that (I've just come upon some articles about that), and I am not sure if
> that would really invalidate cache and help me. What is the right way of
> dong this ? Please, help ...
> ZP.
Exactly what changes in the guest are you talking about? (that are not visible
after
switching hosts).
There was a pygrub caching bug in Xen in EL5, but that shouldn't affect HVM
guests,
since they don't use pygrub.
If you use phy: backend for the disks, then there should be no caching in dom0.
Please paste your /etc/xen/hvmguest config file.
-- Pasi
_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-users
|
Home