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Re: Xen

On Tue, Aug 2, 2011 at 8:46 PM, Alex Goncharov
<> wrote:
> ,--- You/Ben (Tue, 2 Aug 2011 19:38:44 -0500) ----*
> | I am an AVID xen user -- I run my dom0 on NetBSD and also have 2 pleasantly
> | running NetBSD domu's without issue.  And also -- just adding -- I 
> occasionally
> | run a netbsd HVM under Xen's version of qemu to do some testing.
> [ I want to be educated on this ]
> When I researched it a couple of years ago, I came to several
> conclusions on Xen:
>  * A guest of a NetBSD won't use more than one CPUs.

This is being worked on, and I don't mean to flaunt but I was hinted
that there /may/ be decent code
merged into -CURRENT in the coming months.

It isn't perfect stuff, in addition NetBSD currently only has Xen3
support paravirtualized --
I really don't understand the major differences between Xen3 & Xen4
but from what I
can grasp from the Xen community it's mostly bug fixes and relatively
minor improvements.

Now, keep in mind, on the dom0 you can run the Xen4 Hypervisor and
related tools,
and still use the the NetBSD Xen3 Kernel because it's backwards-compatible, but
as much as I wish I could tell you, I have no idea what the
implications of all this are

>  * Xen does not mix well with FreeBSD (I don't remember the details).

This is mostly due to lack of FreeBSD support -- no offense to them -- but
I *think* it's fairly accurate.  I actually have a standing bug with
right now where I can't use FreeBSD as a HVM with more than 1 virtual CPU
(which is odd).  Probably a problem with qemu which isn't xen-specific, or maybe
Xen is just being a piece of crap.  I don't know, and wish I did.
If you'd like to follow that just read my post there, on the FreeBSD
mailing lists.

Otherwise, I have few issues.  That one issue was a doozy, I will admit.
Yes, it's not the cleanest configuration in the world but FreeBSD/xen support is
being worked on fairly actively.  FreeBSD also has experimental PV support but
I've yet to find time to try it.

>    So, of Unixes, only a Linux/NetBSD mixes can be seriously
>    considered.

I've been using NetBSD -CURRENT + Xen for a little over a year for
production servers and maintaining about 98.8% uptime minus some
reboots I'm not counting.  Keep in mind, I said -CURRENT, not -STABLE
which may/may not be more reliable.  I do use Linux guests/domu's on
a daily basis for my own reasons, but *BSD powered stuff just helps
me sleep at night.  Maybe I'm biased, or even ignorant, but it's how
I do business.

>  * I also had frustrating Xen configuration problems when I went from
>    hosting it on NetBSD 4 to NetBSD 5.  Something about network
>    interfaces, IIRC.

It's confusing to comment on this because I don't know if you mean a
NetBSD dom0 or a NetBSD domu, but I'd be happy to help you with any
specific error messages or problems over at the ports-xen@netbsd mailing
list, along with everyone else subscribed there, provided we have time
and the knowledge :)

Out of my domu's (running on a NetBSD dom0),  -- NetBSD and CentOS
are the easiest I've had to configure with both having no issues running
paravirtualized.  OpenBSD actually comes in third, I think, running as a HVM.

OpenBSD for some reason needed model=e1000 in it's vif=[] line, but it's
a quirky little thing in itself.

> Can you comment on any of these points?
> | In my opinion, NetBSD will soon be the choice OS for virtualization.
> Why do you think so?

I think, a simple "plus" of a NetBSD dom0.

> I am no expert, but it seems to me that VirtualBox gets much more
> attention (and is, in my experience, easier to configure and use).
> But VirtualBox is probably not a NetBSD strength, or is it?

Honestly I'm not familiar with VirtualBox, but that big ORACLE logo
turns me off right off the bat.  Sure, Citrix plastering it's logo all over Xen
isn't the highlight of my day either, but at the end of the day, I'll
pick Citrix
over Oracle any day (to be completely biased and generalized about it)

You may also find this petty, but keep in mind Rackspace and Amazon EC2
both use Xen (although, I'm sure heavily modified versions at this
point).  I think
it's safe to say it's fairly proven technology.

> | Just wish it would get there sooner.  I see all kinds of people
> | report problems that they have issues with Xen's networking, Xen's
> | this, Xen's that,
> Precisely what I remember, from the two-three years ago.  Ultimately,
> why fight it, when there are easier options?  I might have been
> impatient, but still...  VirtualBox on FreeBSD worked out of the box.
> Performance was such, though, that I abandoned its use soon, too.  With
> the current modest costs of hardware...

Although I have pretty heavy hardware running my domu's on my NetBSD box,
other than some disk i/o bottlenecks I have, I get pretty decent performance.

Not that I'm satisfied with it.  It could always be better, ESPECIALLY
with the fact
I'm only using 1 out of 4 cores on my systems.

Just use your judgement.  If you're more comfortable with
Linux stuff, well try it.  Linux has KVM, which I know nothing about,
other than the
fact it's a linux-only kernel module.

As I said, I'm also unfamiliar with VirtualBox, which also doesn't
seem to run on
any *BSD.

Then -- there is Xen.  FreeBSD/Xen support, is, as you even said, kind
of shoddy.
The domu support is quirky to say the least and dom0 support is of course
nonexistent.  OpenBSD support is 10 years away (if ever -- kind of out of scope
to elaborate) .. and that leaves NetBSD -- which, in my own possibly biased
opinion is the PERFECT place to get some very decent virtualization.

> -- Alex -- --

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