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xen-devel
Re: [Xen-devel] Migrate/Save of 32-bit domU Broken on Xen 3.1.2 64-bit d
Hi Dan,
Dan Magenheimer wrote:
Joshua --
Why do you need so much memory on dom0? Are you thinking
that the total memory available to guests is limited to
what dom0 has? Or are you running some memory-hungry
applications on dom0?
Hmm, I thought that a 32-bit dom0 system can only have up to 16GB of
memory available to it and its domU's -- and a 64-bit dom0 can have a
max of 32GB. I only allocate ~512MB of memory to the dom0's
themselves. "xm info" shows us the rest of whats available for use by
domU's.
Thus, even if I have 32GB of RAM in a server, the total memory that will
be used in dom0 + all domU's can only add up to 16GB. Am I just plain
old wrong?
Note that 64-bit Xen + 32-bit Dom0 will support both 32-bit
and 64-bit domU's. (Oracle VM uses this configuration by
default on 64-bit capable machines.) And save/restore/migration
has been tested to work for this (with the patch Kurt posted).
Interesting. For some reason I thought that the Hypervisor had to match
the dom0's kernel. So you're saying that if I compile the Xen
Hypervisor as 64-bit and my dom0 + domU's both as 32-bit, I can reach
the full capacity of my servers with respect to RAM (32GB) instead of
being limited to 16GB? (And this only works with Kurt's patches?).
Dan
-----Original Message-----
From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
[mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx]On Behalf Of Joshua West
Sent: Friday, January 18, 2008 4:06 PM
To: Keir Fraser
Cc: Kurt Hackel; xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-devel] Migrate/Save of 32-bit domU Broken
on Xen 3.1.2
64-bit dom0
Dang, doesn't work in Xen 3.1.3-rc1 (like you said/expected), with or
without Kurt's patches.
Hmm... I thought 32-bit paravirtualized domU's on 64-bit dom0's were
supported in Xen 3.1.x? Or am I mistaken?
Perhaps standard features such as start/shutdown/pause of 32-bit PV
domU's on 64-bit dom0's are supported, but not the more advanced
management features like save and migrate - and I was just
unclear from
the beginning?
And of course... the final question that all developers hate... when
s/could one _hope_ (not expect!) to see save/migrate functionality of
32-bit PV domU's on 64-bit dom0's? :-D
Our whole reason for moving to 64-bit dom0's was to utilize 32GB of
memory, instead of the 16GB limitation on 32-bit PAE dom0's. We can't
convert all of our virtual machines (100+) to 64-bit linux as its too
much work and some actually have to be 32-bit due to vendor supplied
software (Oracle, Zimbra, etc). I suppose we'll wait to move
to 64-bit
until [live] migration is available, as its used quite
frequently in our
machine rooms.
Thanks for all of your help Keir and Kurt.
Keir Fraser wrote:
Looking at the issues that need to be handled to support
this, it cannot be
expected to work.
-- Keir
On 18/1/08 22:13, "Joshua West" <jwest@xxxxxxxxxxxx> wrote:
Ahh. Well, I'm building xen-3.1.3-rc1 right now and I'll
see how that goes.
Keir, have you seen this issue before? Where one cannot
xm save/migrate
a 32-bit domU on a 64-bit dom0? Or is this expected to
work and just
doesn't go well for me?
Keir Fraser wrote:
On 18/1/08 22:05, "Joshua West" <jwest@xxxxxxxxxxxx> wrote:
Just to make sure the patches aren't the cause of this new error
message, I'm going to see what happens with Xen
3.1.3-rc1 w/o patches.
Kurt, Keir, everybody else... any ideas as to why "xm
save" (and thus
"xm migrate") of 32-bit domU's does not work on 64-bit
dom0's? Has
anybody found this to be successful in the past?
The extent of the patches that Kurt posted indicate its
pretty unlikely to
work without considerable code modification. I guess
those patches aren't
quite fully baked yet, unfortunately, or haven't been
written with your
precise case in mind.
-- Keir
--
Joshua West
Systems Engineer
Brandeis University
http://www.brandeis.edu
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--
Joshua West
Systems Engineer
Brandeis University
http://www.brandeis.edu
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