On 13 Dec 2010, at 18:28, Ion-Mihai Tetcu <ite...@freebsd.org> wrote:

> I see. Thanks for the time you took to explain things, I'm very new to
> XEN.
> Do we have any docs somewhere (well, except the sources) about our XEN
> support and various options / optimizations? I only know about
> AdrianChadd's wiki pags and http://wiki.freebsd.org/FreeBSD/Xen (which
> are nice, if you happen to know about XEN already and especially if you
> want to work towards a FreebSD as XEN host).
> I guess there are more interested people taht want just to run FreeBSD
> as guest OS (my case).
>> 

The current state of our Xen documentation is ... minimalist. Having basically 
come to it for the first time last week, when we decided we needed to deploy 
FreeBSD on one of our Xen server pools, it's proven pretty hard-going. I have 
some more technical problems to resolve but high on my todo list for the next 
couple of days is documenting what has worked for me on the Wiki (with the 
intent of migrating that to the Handbook once I've confirmed my instructions 
are reproducible!). I also want to drop in at least some stub man pages for our 
PV drivers.

However, more fundamentally, we appear to have some serious functional gaps:

- No ability to use PV drivers under HVM on i386.
- No ability to use a full PV kernel for amd64 (I don't consider this a problem 
for my use though -- HVM on amd64 appears to work well).
- No (obvious) port of Xen guest command line tools to steer ballooning, etc.
- Likely under-testing in certain PV drivers, such as the balloon driver.
- A possible issue with VM migration on PV i386 (we saw panics in local 
testing, but now wonder I it was an unrelated issue relating to different CPU 
types -- more investigation due).
- No event mechanism for blkfront to propagate block device expansion up the 
geom stack, in support of live file system resizing. Right now a destructive 
orphan/retaste is required.
- No live file system resizing support in UFS (does work in ZFS).
- No reference "appliance" images for VM starting points (really requires live 
file system resizing to be useful). This was a top request o our admin folks.

All this said, and after quite a lot of head-scratching, FreeBSD/amd64 seems to 
work well on Xen here a Cambridge, both with and without Xen PV drivers 
compiled in. We need a lot of sanding and polishing but the foundations have 
been usefully laid. And I would agree that documentation is key.

Robert_______________________________________________
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