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RE: [Xen-users] Xen + VServer

> > What advantage does Vserver have compared to Xen ??? why should it
> > make sense to use both?

2 words...

vps resellers.

Whole new market which i'm looking into heavily.

John Fairbairn.

>> Dominique Rousseau Wrote
>> Sent: Friday, 19 August 2005 9:21 p.m.
>> Le Fri, Aug 19, 2005 at 11:12:25AM +0200, Dirk H. Schulz
>> [dirk.schulz@xxxxxxxxxxxxx] a Ãcrit:
>> > >That's great to hear!  Xen and Vserver are IMHO highly complimentary
>> > >and it'd be great to be able to use them together.  The VServer patch
>> > >(last time I checked) was very nicely arch independent but I think
>> > >it's quite a long time since anybody has tried to run it on Xen -
>> well
> done!
>> > >
>> > What advantage does Vserver have compared to Xen ??? why should it
>> > make sense to use both?
> I tend to think of Vservers as basically a "super" chroot on steroids.
> the standard linux chroot mechanism can be broken out of using the double
> chdir(?) method (among others). However the Vserver patch effectively
> provide you with very well isolated environments with practically no
> overhead (mostly owing to the fact that a) all Vservers allocate memory
> from
> the server as needed, rather than being allocated a "chunk" at startup and
> b) on there is only one copy of the kernel running).
>> Vserver makes it possible to share on-disk and in-memory the
>> footprint of a given program between separate contexts.
>> The kernel being shared, if you make your different contexts
>> with hardlinks "copies" of the files, you can have the same
>> code of libc, damemons, ... loaded only once in memory, only
>> the "data" part of memory allocated is charged for each
>> virtual server.
>> So, you get virtual servers that are very efficient on memory
>> and disk usage.
> Yep the higher memory usage is definitely one of the most noticable
> differences when you convert from Vservers to Xen.
> i.e. Instead of lots and lots of Vservers co-existing quite nicely and
> sharing 1GB of RAM, you suddenly find yourself adding more memory to the
> server! But RAM is cheap these days so it's not really an issue.
>> On the other hand, you get less control on the
>> allocation/limitation of ressources used (memory, cpu, ...)
>> and since you have all contexts running in the same kernel a
>> potential security hole ine the kernel would be open to every
>> of the virtual servers.
> The security aspect is my major motivation for looking at moving from
> Vservers to Xen. I imagine that the isolation provided by *BSD's Jails and
> Solaris 10 Zones/Containers would fare equally badly from kernel level
> security holes.
> Whereas you would hope that the extra layers of isolation used by Xen
> would
> protect you better! Not that people won't try to find exploits for Xen
> once
> it gets widely adopted!
> I see that OpenSolaris has been made to boot as a Xen guest by Sun's
> developers. That opens the possiblity of people mixing the two approaches
> (Vserver-like functionality + Xen) as well! Hmm, if Sun ever gets its
> Janus
> project (linux emulation) going you could do something REALLY twisted like
> run your Linux apps in separate secure OpenSolaris Zones inside a Xen
> Guest!
> /shiver
> Anyway... Xen is cool. Vservers are cool. Vservers + Xen would also be
> cool
> but in reality I see Xen being mainlined into the kernel shortly and
> supported WAY more widely so I'm looking at switching our Production
> servers
> from Vservers to Xen. Mostly for ease of maintainence reasons. We run SuSE
> Enterprise Linux 9 and they've going to include Xen in their next release
> (ETA 2006Q1) so rather than mucking about with ANY custom kernel patches,
> etc I will be able to update my Xen server OS's and guest OS's by simply
> connecting to their update server!
> Less effort to stay patched = Heaven (at least in my books!!!)
> Cheers
> Mike
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