Hello, On the wait for RHEL5 we''re considering to move some of our servers under Xen. So few questions appeared. :) - how to "clone" domU server? With posibility to change IP address, turn off some services before start. - is it possible to allow domU server to access some specialized PCI card? E.g. some telco card or Dolphin SCI card for MySQL Cluster? - is there some advantages for running Linux/Linux combination on VT/Pacifica enabled CPUs? - what "part" of OS has the biggest performance hit running under Xen? Disk operations? Process scheduling? Network latency? Or something else? In HP EVA best practices guide I read that for perfomance one have to create as few LUNs as possible. But if for every domU server I''ll create separate LUN the number of LUNs will be quite high. Is it possible to reduce this number and still retain live migration capability and store domU server''s data on SAN? Thanks, Mindaugas _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On Thursday 16 November 2006 12:29 am, Mindaugas wrote:> - is there some advantages for running Linux/Linux combination on > VT/Pacifica enabled CPUs?no, at least not yet. :-)> - what "part" of OS has the biggest performance hit running under Xen? > Disk operations? Process scheduling? Network latency? Or something else?all IO is affected. it''s not a heavy burden on Dom0, but the domain switch adds to the latency. i guess (no benchmarks done) that network might be hit worse than disk IO, because disk can (in theory) use bigger chunks of data on each operation.> In HP EVA best practices guide I read that for perfomance one have to > create as few LUNs as possible. But if for every domU server I''ll create > separate LUN the number of LUNs will be quite high. Is it possible to > reduce this number and still retain live migration capability and store > domU server''s data on SAN?use a single LUN and split it via LVM. better make it CLVM, so you can administer it with all nodes online. (has anybody done it with clustered HA/EVMS?) -- Javier _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On Thu, 16 Nov 2006, Javier Guerra wrote:> On Thursday 16 November 2006 12:29 am, Mindaugas wrote: > > - is there some advantages for running Linux/Linux combination on > > VT/Pacifica enabled CPUs? > > no, at least not yet. :-)Speaking as a Xen noob, surely the answer to this is ''yes'', and not ''no''. It''s not possible to run an unmodified (not Xen-enabled kernel) guest otherwise. If all you want is to run Xen-enabled guests, then the answer is ''no''. Do I misunderstand how this works? Steve _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
> -----Original Message----- > From: xen-users-bounces@lists.xensource.com > [mailto:xen-users-bounces@lists.xensource.com] On Behalf Of > Steve Thompson > Sent: 16 November 2006 13:01 > To: xen-users@lists.xensource.com > Subject: Re: [Xen-users] Few questions about Xen > > > On Thu, 16 Nov 2006, Javier Guerra wrote: > > > On Thursday 16 November 2006 12:29 am, Mindaugas wrote: > > > - is there some advantages for running Linux/Linux > combination on > > > VT/Pacifica enabled CPUs? > > > > no, at least not yet. :-) > > Speaking as a Xen noob, surely the answer to this is ''yes'', > and not ''no''. > It''s not possible to run an unmodified (not Xen-enabled kernel) guest > otherwise. If all you want is to run Xen-enabled guests, then > the answer > is ''no''. Do I misunderstand how this works?I think this is all depending on how you define "advantage". The advantage with HVM (hardware supported virtualization) is that you can just use the binary as it comes on any Linux CD, without it specifically supporting Xen. The advantage with Xenified linux is that, although it may need some configuration changes to be applied before compiling a new kernel, it allows faster interaction between the virtualized hardware and the actual hardware (i.e. para-virtual network driver is "faster" than HVM-emulated driver [unless you start introducing PV-drivers in the HVM domain] - I say faster in quotes, because it is actually more correct to state that the HVM emulated driver needs more CPU POWER to perform at the same level, and today you may not even be able to get to the same level, but it is a question of CPU power to achieve that...). Just like so many other things, there are advantages and disadvantages with just about anything. A Ferrari is a lovely sports car, but try moving a full-size 19" computer rack using a Ferrari and you''ll see that it''s also not so good at some things... ;-) -- Mats> > Steve > > _______________________________________________ > Xen-users mailing list > Xen-users@lists.xensource.com > http://lists.xensource.com/xen-users > > >_______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On Thu, 16 Nov 2006, Petersson, Mats wrote:> I think this is all depending on how you define "advantage".Yes, you are right of course. My point was that if you *have* to run an unmodified kernel (such as for Redhat 7.3, or Windows, etc), then unless you have HVM you cannot do it at all. That''s what I meant by "advantage" :-)> A Ferrari is a lovely sports car, but try moving a full-size 19" > computer rack using a Ferrari and you''ll see that it''s also not so good > at some things... ;-)I''d like to get the chance to try, nonetheless! Steve _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users