iSCSI and clustering with FreeBSD

[Andy Sporner]

Michael Grant wrote:

>It looks like no matter what I do, I need a second box next to the
>first one to redirect packets to the other box if one of the boxes
>goes down.  I'd probably do this with NAT or an ip tunnel.  This
>second box almost makes it seem not worthwhile to put the other boxes
>in different ISPs.  Anyone have better ideas?
>
>  
>
This is only a problem with migrating processes.  A long time ago (and 
if you do
a search in the IBM "linux" knowledgebase you might find it (ca 1996)) 
that a
resolver protocol would be a good idea that is application based.  Kind 
of like
a DNS for applications.    This would solve the problem.  I had the idea 
to actually
make a patch that would put this into the "connect" primitive in the 
socket layer so
that it would be transparent to the user.  HTTP redirect does most of 
it, but not every
thing.

For process Migration it is a problem however, since each machine at a 
minimum has a
unique IP address.   Therefore some sort of translation is needed to 
balance the traffic.
If there be risk seeking beta testers there, I have somewhere handy a 
version of my software
that has a load balancing NAT in the kernel.  It is limited to TCP in 
the moment.  There are
some other minor limitations as well which are in the process of being 
fixed.  But if anyone
wishes to try it, send me a mail and I will send a small (~200K) tar 
file with code.

In short, I think as long as you wish to redirect applications you are 
sort of stuck
with a middle box.  Either that or get a special kind of ethernet switch 
that does this
(ahem ahem ahem... ;-) in hardware and then you don't waste a computer.


Andy