Subject: Re: [vserver] VServer vs OpenVZ.
From: "John A. Sullivan III" <jsullivan@opensourcedevel.com>
Date: Thu, 09 Dec 2010 15:11:35 -0500

On Thu, 2010-12-09 at 14:59 -0500, John A. Sullivan III wrote:
> On Thu, 2010-12-09 at 19:31 +0000, Gordan Bobic wrote:
> > On 12/09/2010 06:14 PM, mourad.alia@orange-ftgroup.com wrote:
> > > Dear VServers,
> > >
> > > As introduced in my previsous post, wa are about using VServer to emaulate P2P
like VoIP peers. This is used for sacalability and performance testing of our VoIP application.
> > >
> > > Here are our needs :
> > >
> > > A) We want to have a maximum of VMs per server. Our server are 24 hyperthreded
machine with 6 physical network interfaces :
> > >      IP Network Server NSN2U (Ballenger-NH)
> > >      Single 600W AC PSU
> > >      Memory 24 GB
> > >      CPU Dual Xeon E5645
> > >      SATA HDD 500GB
> > >      Ethernet I/O Module (four Gigabit rear ports)
> > >
> > > B) Each VM hosts a JVM which run one or many instances of our applications.
> > >
> > > C) The applications (VoIP peers) communicate basically through multicast.
> > >
> > > D) Each n VMs (m applications) will use one given Eth physical interface to distribute
correctly the network traffic.
> > >
> > > Currently, there is a hot discussion in my departement on OpenVZ vs VServer :
" VServer is more tooled, simpler, virtualise the network, supports hot VM migration".
> > 
> > AFAIK, vserver doesn't support live/hot migration of VMs. Do you really 
> > need it, though? Startup time on my VMs (based on RHEL6) is on the order 
> > of 5s for the complete system including services (mysql, apache, etc.).
> > 
> > > What do you think about this versus ?
> > >
> > > Any particular advise towards my use case ?
> > 
> > The absolute killer feature of vservers for me is hashify. In a 
> > nutshell, it adds a feature to provide copy-on-write hard-links, which 
> > means that once you have hashified your guests, all the DLLs have the 
> > same inode number and mmap into the same memory. That means that if you 
> > have 100 guests running the same base setup, you don't have 100 
> > instances of glibc wasting RAM, but only one. On top of that, since 
> > identical files are hard-linked, it makes the cache efficiency much 
> > greater. This means you can overbook your memory way, way more than you 
> > otherwise could and gain some performance at the same time.
> > 
> > Gordan
> I concur exactly.  We debated heavily between the two.  OpenVZ did seem
> to have more commercial refinement and we were concerned at the small
> developer pool for VServer.  The two things that won us over to vserver
> were that it is truly and fully open source rather than an excuse to
> upsell into a commercial version and hashify as Gordan pointed out -
> John
> 
I should mention that I believe hashify is available for OpenVZ but as a
commercial add-on - John