I have a backup running on four Windows HVM domains (I know you asked
for someone using PV domUs, but these are running on the PV network interfaces,
as I am using James Harper's GPLPV drivers). All four DomUs are on the same
Dom0, which has one gigabit connection. The backups are going toward a
separate physical backup server. Here is a summary of said backups:
HVM1:
Start backup objects time 09/05/2008 1:11:04 AM
Elapsed backup objects time 2 hours,14 minutes,30 seconds
Completed 61743 objects, 9.33 GB (100%)
HVM2:
Start backup objects time 09/05/2008 2:18:36 AM
Elapsed backup objects time 57 minutes,30 seconds
Completed 38071 objects, 6.05 GB (100%)
HVM3:
Start backup objects time 09/05/2008 2:21:41 AM
Elapsed backup objects time 57 minutes,15 seconds
Completed 36175 objects, 5.94 GB (100%)
HVM4:
Start backup objects time 09/05/2008 1:17:47 AM
Elapsed backup objects time 1 hour,30 minutes,30 seconds
Completed 36101 objects, 5.92 GB (100%)
As you can see, these backups overlap, so the network usage across the
bridge/NIC would be even higher than what it takes to back up 6 GiB in just
under an hour (I suspect that is quite a bit more than 3.6Mbps, but I haven't
calculated or benchmarked). Also, as you can see here, they have been running
for some time:
[virtadmin@virt1 ~]$ sudo /usr/sbin/xm list
Name ID Mem VCPUs State Time(s)
Domain-0 0 2858 4 r----- 160986.6
xm1 17 2048 1 ------ 233816.8
xm2 18 1024 1 -b---- 188676.6
xm3 19 1024 1 -b---- 166046.2
xm4 20 1024 1 -b---- 171760.6
[virtadmin@virt1 ~]$ uptime
10:50:40 up 65 days, 20:45, 1 user, load average: 0.00, 0.01, 0.00
The DomUs are currently IDs 17-20 because of reboots for software
installs, updates, and whatnot. xm1's output from systeminfo shows it has been
up for 17 Days, 18 Hours, 24 Minutes, 31 Seconds. This is with the backup
mentioned above running 5 times a week.
Anyway, I am running Fedora 8 with a kernel from their repo. I have
attached the .config for that kernel in case you want to compare. The version
matches yours, but it's hard telling what additional patches the Fedora kernel
might include (though technically said patches would be available with the
source, which should be downloadable from multiple mirrors, so I guess it's not
so hard telling). Hope this is helpful,
Dustin
-----Original Message-----
From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
[mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Paul
Sent: Thursday, September 04, 2008 18:43
Cc: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-users] Re: domU network fails under load - vif breaks
>
> On Sep 1, 2008, at 8:57 AM, Paul wrote:
>
>
>
> At a certain point that I have not established exactly, the
> network load takes out the pv network. For example, if I initiate
> a bittorrent session in a pv domU, I get a slow build up of
> network load, and then connectivity is lost to both of the pv
> domU's. If I console into them, they cannot ping outside the
> network, but they can ping their own interfaces. A tcpdump on the
> dom0 physical shows no traffic. However, during all this, the hvm
> domains are able to use their network connections without issues.
>
> I have experienced the same issue with Ubuntu 8.04. The only solution
> I have found is to limit the rate of the nic so that it doesn't reach
> a transfer rate that breaks the networking.
> Pepe
>
Thanks Pepe. My last test showed the network breaking at 3.6Mbs - too
slow to lower the nic rate, and having networking running that slow
would make the vm unusable for its purpose.
I have upgraded Xen from 3.2.1 to 3.3, and the problem remains, which
means I have changed:
1) Change domU kernel (2.6.21, 2.6.24, 2.6.25)
2) Change domU userland (gentoo, ubuntu)
3) Change dom0 physical nic + driver (Realtek 8169 -> 8168)
4) Change Xen version (3.2.1 -> 3.3)
The only thing I haven't changed is the dom0 kernel. I am using a stock
2.6.21-xen gentoo kernel, so it would be great if anyone watching this
that has pv domUs working under a 2.6.21 kernel would post their .config
so I can compare it to mine.
Thanks,
Paul
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