Somewhere out there!

Until today I hadn’t taken the time to upgrade to the latest Xen 3.0 testing. Here’s a quick note if you keep getting this error and can’t figure it out: ERROR: Xen will only load images built for Xen v3.0.

Make sure you have:

kernel /xen-3.0.gz dom0_mem=262144 com1=38400,8n1

instead of:

kernel /xen-3.0-devel.gz dom0_mem=262144 com1=38400,8n1

Technorati Tags: xen

Some useful hints for running Debian/domU from the Xen Wiki:

I encountered the following problems when setting up Debian 3.1 as a DomU on Xen3.0 Unstable for the XenDemoLaptop:

1. When booting, I get “Couldnt get a file decriptor referring to the console” about 100 times.
• Fix: Remove /etc/rcS.d/S05initrd-tools.sh
2. When booting, I get lots of “FATAL: Module blah not found”
• Fix: Remove offending modules from file /etc/modules
3. When booting, after it says “Starting hotplug subsystem:” some of the say “[failed]”
• Fix: Move offending modules out of /etc/hotplug/

Sun’s released ZFS for OpenSolarias and it looks very cool. Couple of flash demos show how easy it is to manage and its selfhealing abilities.

It would be very interesting to see the possibilities of this combined with OpenSolarias acting as a dom0.

I seem to be doing this a lot at the moment. So I’ve collected a few notes together as reminder of the process.

Had a difficult week testing Xen 3.0 on my new v20z dual Operton machine.

Seems I was missing hotplug, which Xen 3.0 needs installed into domO in order to initialise the creation of block devices correctly. I’ll have more to report once I’ve got NX going, plus a 64bit domU guest.

A useful comment about a networking issue with Xen. Something I’ll have to try out at some point.

On a separate but still networking issue, I noticed that my XenU’s outbound traffic is sporadic (between 800KB/sec and 2MB/sec). The problem is the default qdisc being inadequate. So I fix it with:

XenU# tc qdisc add dev eth0 root tbf rate 50mbit latency 20ms burst 50k

TBF requires kernel option CONFIG_NET_SCH_TBF, but other qdisc should work too if the buffer is large enough to handle the bandwidth. To make this permanent, add it as a ‘up’ line to iface eth0 in XenU’s /etc/network/interfaces.

I’ve just moved into a new center, combined with this change I’ve fixed a Xen configuration [1] bug that has been plaguing this site with timeout errors. The addition of SunFire V20z at the end of the month should also improve performance, and also allow me to take my Xen/NX desktop testing to the next level.

[1] vif configuration error where 00:01:00:101 and 00:01:00:01 resolve to the same 00:01:00:01 MAC. The former should be 00:01:01:01.

On Friday my NX desktop started playing up a little. So I rebooted. Kernel root VFS mount error! Very nice. After some testing, it was the first time I’d seen a faulty HDD bring down the Linux kernel even when booting from a Live CD rescue disk. Damn!

Luckily, I was using NFS home directories and avoided “where is that month old backup” mode.

One of my goals with NX and Xen is to achieve Thin Guy‘s level of desktop support. Zero!

Sun Ray = Office Supplies. You can’t “Fix” a Sun Ray. Out of the 33,000 Sun Ray desktops inside of Sun, how many “desktop” techs do you think are required to manage that install base? How does the number zero grab you? On the ultra rare occasion that something happens to your Sun Ray (let’s say a power supply failure), you replace it and send it back for a warranty replacement (5 years on the SR1g). In the meantime you walk to the closet, grab a spare and plug it in and pick up exactly where you left off. Anyone who can replace staples in a stapler or replenish their supply of post-it notes can replace a Sun Ray

MARC: msg ‘Re: [Xen-devel] BVT scheduler settings examples’:

xm bvt takes the following arguments:
DOM – domain id
MCUADV – inverse of weight. Therefore if you want to give more CPU decrease MCUADV

WARPBACK – boolean, enables domain to execute before other domains after waking up, decreases lattency, useful for driver domains
WARPVALUE – the bigger the value the greater number of domais will be preempted
WARPL – if warpback is enabled, limit the time that it is enabled for
WARPU – after warping was disabled by WARPL enable it again after WAPRU

So if you want 30/70 you can do the following:
xm bvt 1 47 0 0 0 0
xm bvt 2 20 0 0 0 0
(since 47/20 ~= 2.33 and 70/30=2.33) the MCUADV is integer, so in order to increase the granurality you can give bigger values. Only the relative value matters.