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On Tuesday 03 July 2007 15:31, Joseph Mack NA3T wrote:
> On Tue, 3 Jul 2007, Rio wrote:
>
> >> You have one box which is running 84 instances of a virtual
> >> server and another box which has 40 instances. So you have
> >> two boxes which can appear to be 124 realservers?
> >>
> >
> > to the outside world (not admins) the 124 virtual servers appear to be
> > individual discreet servers. i think i may be confused by the term
> > realservers.
>
> realserver is an LVS term referring to the machine/node(s)
> that are being loadbalanced by the director.
>
> I've never liked the LVS nomenclature; e.g. "virtual",
> "realserver", but since I couldn't come up with an
> alternative and no-one else seemed to mind, I've just
> accepted it. We haven't had too much problems with the word
> "virtual" since we haven't run into other projects using the
> term much. However if realservers are going to be
> virtualised, there's going to be lots of name space
> collisions.
>
ah ok. so then realserver is a name for whatever 'server' be it a dedicated
machine or virtual that lvs manages. so then yes, in terms of lvs each server
that lvs will be handling, although they will be linux-vserver virtuals, is
a 'realserver' in terms of lvs.
> >> so you have 84 virtual machines but they don't appear to be
> >> 84 individual machines?
> >>
> >
> > i was comparing the context oriented virtual servers using
> > a single master kernel on the host to 'virtual machines'
> > such as that presented by vmware with their own virtual
> > hardware requiring complete o/s installs with kernels,
> > modules etc.
>
> Gerry has straightened me out here.
>
> >> what are "context virtuals" (nothing useful found in
> >> google).
> >
> > bad description :) each of our virtual servers runs in its
> > own 'context' (unique number). i think the description
> > from the linux-vserver website says it much better than i
> > possibly could:
>
> OK, better go look these up. Better go look at the OpenVZ
> project docs too.
>
> > 2 of them plus the new one to be added are tyan gx28
> > servers with 2 dual core opteron processors giving it 4
> > cores, 16gb ram. one server has no need for more than 2
> > nics so the 3 on-board are sufficient, but the other one
> > uses the 3 built in nics plus a 4 nic card. this serves 5
> > discreet networks in addition to our pvtnet and our own
> > public net. when we change over to mirroring/lvs control
> > we will add nics to make all 3 servers identical.
>
> The hardware then is a 4 core box. Since the dual core
> opterons don't have any more memory bandwidth than the
> single core CPUs, you can only use both cores at the same
> time if one core is running its application in L1/L2 cache.
> I don't know what service you're planning on balancing, but
> since most people use LVS for loadbalancing http, let's talk
> about http. (since http is just fetching pages from disk
> cached in RAM, I don't expect you'll get much for your two
> cores). My original question then is (using Gerry's
> nomenclature)
i am more looking at load balancing the data streams so that one machine isnt
handling 70% or 80% of the data load at the ethernet card. lvs will not help
the 'load' on the processors much since that is reasonable anyway. these
machines are not loaded down, we are simply looking for redundancy, load
balancing/sharing the load on the web server itself and failover. there are
of course many other services this will be applied to as well.
>
> o How many httpd realservers would you choose to run as VEs
> on this box and why do you choose that number? ie why don't
> you run just one VE realserver?
>
because one web server handling all these websites is a literal mess in
organization. one company has their own virtual server because we host 36
websites for them and we wanted to stick them all together... we
place 'dangerous' type web admins in separated servers so if they mess it up
it doesnt affect the rest of them. a single server would affect them all.
other customers, due to one reason or another have their own virtual server
and they host a number of their own sites. we have one web server for
our 'generically safe' customers which hosts 400 domains and is namespace
only so we do glob domains together when it is safe otherwise we protect all
our customers from the unsafe ones, or if they have a number of sites, we
place them in one server. another reason for making it by customer when they
host a number of their own sites is ease of shutting them off if they dont
pay. i simply do vserver <servername> stop and thats all there is to it. i
dont have to hunt individual sites and disable each one.
another reason for using a number of VE as everyone is calling it is if i
decide i want to move a service to a different machine, i simply move the
entire virtual server over and start it on the new machine and it is done. no
playing with o/s configs or anything. the only thing that gets involved is
machine architecture change such as moving a virtual from an amd64 to an
intel processor i686 machine but since we no longer have that issue to worry
about it is simple.
> Joe
> --
> Joseph Mack NA3T EME(B,D), FM05lw North Carolina
> jmack (at) wm7d (dot) net - azimuthal equidistant map
> generator at http://www.wm7d.net/azproj.shtml
> Homepage http://www.austintek.com/ It's GNU/Linux!
>
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--
Rio
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