Re: second squid box for redundancy and load balancing

On Tue, Dec 21, 1999 at 09:31:12PM +0100, Henrik Nordstrom wrote:
> Jay Wilson wrote:
> >
> > Has anybody setup a second local squid box for redundancy and to share the
> > load?? I don't see any documentation on the FAQ's for it. What is involved??
>
> The cheapest solution (unless you have a huge amount of clients where
> the cost of reconfiguring sums up) is to use a proxy.pac script.
>
> Another way is to use DNS load balancing, with a "smart" DNS server who
> automatically removes a failed cache from the DNS entry.

A problem with this is that until the old DNS entry expires, some
clients can be sent to a now-down server, so it doesn't give you
complete fail-over. There *is* a generic workaround for this involving
scripts to have the servers "buddy" each other in pairs, by checking if
the other server is still up and ifconfig'ing the other's address if it
isn't. Then you have to add another script to listen for ARPs and
release the address if it sees the other server come back up.

 
> The more advanced way is to use a TCP loadbalancer, for example Cache
> Server Director from RadWare or a Alteon switch or similar equipment.
> However, this costs a bit and have problems of their own, but it is
> quite nice when it works.

The biggest advantage of switches/routers over servers is: no moving
parts, so they don't go down because a hard disk failed. The second
one is (somewhat) simpler software because they're doing a more limited
list of things. (A third is that they reboot a lot faster.) Overall I
tend to figure downtime for servers will be about 1 order of magnitude
higher over the course of a year, than for a reasonable router or smart
switch.

  -- Clifton

-- 
 Clifton Royston  --  LavaNet Systems Architect --  cliftonr@lava.net
        "An absolute monarch would be absolutely wise and good.  
           But no man is strong enough to have no interest.  
             Therefore the best king would be Pure Chance.  
              It is Pure Chance that rules the Universe; 
          therefore, and only therefore, life is good." - AC