Re: [Xen-users] Dom0 Crash - High Network Load - Debian Lenny Xen 3.2-1

[Andrea Janna <acq5meteor@xxxxxxxxxxxxxxxx>]

-------- Original message --------
From: Thaddeus Hogan <thaddeus@xxxxxxxxxx>
Date: 05/11/2009 17.01
> I'm looking for a place to start with a problem I am having where I think
> high network load is crashing my Xen host. Any help you can offer is
> greatly appreciated!
>
> I started having an issue with my dom0 crashing when under very high
> network load. I discovered this when I ran a large backup (1.7 TB) on a
> domU.
>    
I had a similar problem last month. I'm running a Debian Lenny dom0 with 
3 Lenny domUs. Kernel 2.6.26 and all software packages are Lenny releases.
I use Bacula for backups on a DAT 72 tape device. Dom0 is running Bacula 
storage daemon, which manage the DAT device itself.
If I run a domU backup (Bacula file daemon running in domU and sending 
data to dom0 over IP, Xen bridged networking) the system becomes 
unstable after several minutes of backup. Sometimes dom0 crashes and 
reboots. Sometimes domUs IP network stops working.
If I don't perform domU backup the system is stable.
If I run a backup of another computer (Bacula file daemon running on a 
Windows box), Lenny computer remains stable. So I suppose issue is 
related to higher disk activity when Bacula file daemon is running in 
domU. Dom0 and DomUs share the same physical disk, a SATA soft raid5 
array. When I run a backup of a Windows computer data is sent to Bacula 
storage daemon in dom0 via IP ethernet network and Bacula storage daemon 
writes that data on tape.
I didn't have time to investigate further, cause I needed the system 
working for production.
I solved this issue installing Xen 3.4 (back-ported from Debian Squeeze) 
and Suse Linux Enterprise 11 kernel 
(http://wiki.xensource.com/xenwiki/XenDom0Kernels) on dom0 only.
Be aware that on Suse kernel some Xen networking features are compiled 
as modules, so you need to load them before starting domUs.


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