[Xen-users] dom0 freezes under high IO load

[bigfoot29 <bigfoot29@xxxxxxxxxxxxxxxxxxxxxx>]

Heya. :)

Just wanted to second dom0 - crashing behavior.

Due to the fact that I have had never the same problems with 2.0.7 (and
at least the same CPU/network utilization -> HDD-utilization should be
compareable) I can second that with 3.0.x the behavior of dom0 got bad.

Normal uptime with 2.0.7 was up to 2 months; with 3.0.x its pending from
24 hours up to a week.

2 interesting things to mention:
1st: When the whole system had crashed (domains also had to be started
new) the Xen-System stays up round about a week. When I just reboot the
server (and thus Dom0 with frozen domU's while reboot), server dies more
often.
2.nd: I tried to create a simple 2 GB file using dd if=/dev/zero of...
inside(!) a vm, and it froze the system right at the beginning of file
creation.

All VMs are running using files as virtual harddisks; so basically it
are no processes that do anything "special".

All running VMs are paravirtualized ones - no HVM guests.

However, its weird that I can't use swap inside a dom0 - you can bet
your soul on the fact that as soon as you reduce the mem (192MB maybe)
and you have processes that want to swap out, your Dom0 WILL crash - not
right away, but soon enough.

So basically if you want to increase Dom0 livetime, you gotta increase
memory dedicated to dom0.

Never had THESE issues with vanilla kernels (or as mentioned the 2.0.7
ones)

Funny thing: with a Dom0-machine just staying ready for action and
running a samba fileserver (well, its a backup server that could run a
VM if needed where I didn't want to put the sambaserver in a VM) I get
the same behaviour - all 2 weeks the dom0 just gets unresponsible when
you want to access hdd.

Please, don't start something like "well, its not supposed to run this
or that inside a dom0" - I can't export it to a VM as long as I can't
make sure I can access the data in the VM whenever I need them. I don't
want to do a Backup-VM-Recovery just to recover the other vm's data...
So for a small company you have to rely on some backup mechanisms or
that sorta stuff. Paying 2-5000 dollar just to get a dom0 working that
shouldn't have these child illnesses (sorry to call them that way... I
think its just a bug that needs to be fixed)

So thats no insult on the Xen-Devs... just a plea to fix it. When I can
help, lemme know.


Regards, Bigfoot29


On So, 2007-03-04 at 11:19 +0100, xen-users-request@xxxxxxxxxxxxxxxxxxx
wrote:
> dom0 freezes under high IO load

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