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Re: [Xen-users] Changing MTU of vif

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Subject: Re: [Xen-users] Changing MTU of vif
From: "Phillip Bennett" <phillip@xxxxxxx>
Date: Sat, 26 Apr 2008 11:15:16 +0100
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"Tracy R Reed" <treed@xxxxxxxxxxxxxxx> Wrote:


Phillip Bennett wrote:
I would put a line somewhere in your startup (after the network is up) to set the MTU. It can be done on the command line using the ifconfig command.

You mean in the network startup in the DomU? That won't change the MTU on the vif in the Dom0. I do have it set inside the DomU to be set to 9000. I can do it on the command line in the dom0 after startup but that is a real pain and has the nasty consequence that your disk behaves very unreliably until you look through that long list of vifs and figure out which one belongs to your domU and connected to the storage bridge and manually change it. Not acceptable.


I see your problem. I had the impression you were exporting the hardware to the DomU. (I guess that's what I am going to do, I just assumed) I guess actually finding the interface you need would be a lot harder.. I haven't had to do this, so can't offer anything useful.


BTW, which AoE unit are you using (presuming it's Coraid)? Is it the 15xx series, or the 16xx series? I'm looking at buying one this week and would be very interested in how it performs in this type of setup.

Neither. I have built my own. A supermicro 3u 15 drive case with triple redundant power, an Intel mobo with Intel cpu and 2G of RAM, and a pair of Gig-e network cards bonded with 802.3ad, and an Adaptec 31605 RAID controller. I run qaoed on it by just slicing off a piece of disk with LVM and point qaoed at the lv. I have two of these set up identically and the dom0 does software mirroring between them. So I could have a network link fail or even a whole disk server fail and not have any problems.

I purchased a couple of the Coraid units about a year ago and found that their implementation of LVM is not flexible enough. It can only export whole disk devices and cannot export just a 50G slice of disk which is what I need. So I had to send them back. They don't run Linux and Linux's LVM in their Coraid units. They run Plan 9.

That sounds like a sweet setup! Do you think it's faster than the Coraid units then? How is it pricewise? (I'm guessing it's a LOT cheaper...)


<offtopic slightly>
I'm looking at buying a new server and passing the AoE functions through to one or more DomU's via exported ethernet interfaces (I will have 6 or so) If it's not feasable, I would love to know BEFORE I buy it. :)
</offtopic slightly>

AoE with Xen works perfectly for me. The only problem is that it is rather challenging to set up. You should be a pretty experienced sysadmin to get it going.

Fair enough. I'd say I'm faily experienced... Hopefully enough to get it up and running satisfactorily. :)

I have set up a website at http://xenaoe.org where I am documenting my whole setup and promoting the idea. I still need to get my initrd up there (pretty custom, diskless cpu nodes, etc.) and a number of other fixes and optimizations which I have made. It has been a LOT of work to get it all going. So I am working to share everything I have learned with the rest of you folks so you can set this up also.

Looks great. I'll be sure to read it regularly. Good Luck!

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