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I’ve been battling lately with a lot of problems with cman, part of Red Hat Cluster Suite. Specifically, the fencing tool (fenced) is pretty much junk when you try to start using it with Xen dom0′s. After much searching and gnashing of teeth I happened upon this mailing list post. The promise there is that you could take clvm and compile it against openais and get a cluster aware LVM which doesnt require the rest of Red Hat Cluster Suite (and its crappy documentation, crappy fencing, and general all around crappiness). A little more searching turned up this web site from Olivier Le Cam which pretty much did 90% of the work for me.

After some testing I’m happy to say it appears to work smashingly. What follows is a somewhat more complete version of how to achieve the same results on Debian Lenny. Enjoy :)

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Recently I came upon the need to do all my network routing and firewalling inside a Xen domU. I am not the first to do this but I thought I’d do a little write up on it to help others trying to accomplish the same thing in Debian.

The idea here is to end up with (at least) two VLANs on the network with the dom0 and domU’s being able to choose one or both networks on which to exist. In the case of both, you can set up a handy domU firewall/gateway :)

As you can see from the diagram above, we will end up with three bridges in the dom0 with all the appropriate glue to tie everything together. Best of all, this is all assembled on the fly during bootup.

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Performance and failure testing are next up in building our kickin’ iSCSI/AoE device.

The Debian Etch installer supports building and installing onto software RAID arrays. Because of that…

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Todays adventure with building a SAN on the cheap involves attempting to get hotplug working and changing device mappings.

First of all, hotplug. I have discovered that…

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AoE (ATA over Ethernet) and iSCSI are the hot new things. Xen is the hot new thing. I like using hot new things as long as they can be made rock solid.

There happens to be a company (Coraid) that makes a turnkey AoE device. Its far cheaper than a true fibre channel SAN or something similar. Perfect for setting up a SAN over Ethernet device that can serve Xen domU filesystems out to “thin” dom0′s on the network.

Well that’s all well and good but you see I’m always looking to save a buck…

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