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Re: Apache clustering w/ load balancing and failover

On Wed, 2003-09-17 at 15:00, Shri Shrikumar wrote:

> Looking at the documentation for LVS, it mentions that it needs two
> nodes, a primary node and a backup node which then feeds into n real
> servers. 

Actually I never saw this mentioned in the documentation - I haven't
looked at it for quite some time now, tough.

LVS definitely works with ONE machine which acts as the loadbalancer.
You can use a second machine for failover if you need the redundancy,
but as far as I know, LVS can't handle this by itself so you would have
to use keepalived or heartbeat for that.

The balancer hardly needs any resources - if it wasn't for the quality
of the hardware (i.e. you don't want to see your balancer die and take
the whole farm offline because of some el cheapo motherboard) you could
use any old Pentium lying around to handle quite a bit of traffic.
Even the cheapest Celeron rackserver can probably handle some hundred
Megabit throughput...

To sum it up:
You take some machine which will act as a loadbalancer and distributes
the HTTP (SMTP/POP/...) requests to you pool of real-server.
To achieve this, patch your kernel or load the ipvs modules.
Define a service and add real-servers...

If you build some high-performance and/or high-availability farm with
this setup you should also consider some other things (i.e. planing the
cluster environment so you don't run into bottlenecks later), but for a
first test-setup you could probably start right away...

If you have further questions, we can discuss details off-list as I may
become OT.

best regards,
  Markus Oswald
Markus Oswald <moswald@iirc.at>  \ Unix and Network Administration
Graz, AUSTRIA                     \ High Availability / Cluster
Mobile: +43 676 6485415            \ System Consulting
Fax:    +43 316 428896              \ Web Development

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