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On Mon, 6 Mar 2000, Nissim wrote:
> I'm curious about the physical architecture of a cluster of servers
> where "the realservers have their own route to the client." (Like in
> LVS-DR and LVS-Tun) How have people achived this in real life? Does
> each real server actually have it's own dedicated router and Internet
> connection? Do you set up groups of real servers where each group
> shares one line?
It could do or it can share things. We've got 3 LVS based clusters, based
around VS-TUN. The reason for this is because one of the clusters is at a
different location (about 200 miles from where I'm sitting) , and this
allows us to configure all the realservers in the same way thus:
tunl0:1 - IP of LVS balanced cluster1
tunl0:2 - IP of LVS balanced cluster2
tunl0:3 - IP of LVS balanced cluster3 (remote)
The only machines that ends up getting configured differently then are
just the directors.
So whilst machines are nominally in one of the three clusters, if (say)
the remote cluster is overloaded, it can take advantage of the extra
machines in the other two clusters, which then reply directly back to the
client - and vice versa.
In that situation a client in (say) Edinburgh, could request an object via
the director at Manchester, and if the machines are overloaded there, have
the request forwarded to London, which then requests the object via a
network completely separate from the director's and returns teh object to
the client.
That UK Nat cache likely to be introducing another node at another
location in the country at some point in the near future which will be
very useful. (The key advantage is that at each location we gain X more
Mbit/s of bandwidth to utilise making service better for users.)
This is only one example though - there's plenty more possibilities.
Michael.
--
National & Local Web Cache Support R: G117
Manchester Computing T: 0161 275 7195
University of Manchester F: 0161 275 6040
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