Re: Speaking about pure fail over - what about pen itself ?

From: Dominic Marks <>
Date: Mon, 27 Mar 2006 23:03:24 +0100

Ricardo Stella wrote:
> Dominic Marks wrote:
>> Ulric Eriksson wrote:
>>> On Mon, 27 Mar 2006 wrote:
>>>>> I'm only looking at two boxes, except that they will also balance
>>>>> other
>>>>> services located elsewhere. Should the separate interfaces that pen
>>>>> listens to (not the shared one), be real or can they be virtual ?
>>>>> Also, if going with independent LB boxes (such as the original
>>>>> example),
>>>>> do they need to be powerful boxes ? TIA...
>>>> A simple and cheap way to do failover for pen would be using
>>>> failover at the DNS level - with a service like
>>>> Zone Edit (
>>>> ZoneEdit can test if the server is up and if it is not, it can point
>>>> your domain to a different IP possibly on a different network.
>>> I'm positive that can't work. The old address will be cached on
>>> several levels throughout the Internet and there is no way to clear
>>> all those caches from a central point. If they charge money for the
>>> service, it's a hoax. Otherwise it's just silly.
>>> Multicast in Linux isn't very reliable (or I'm simply incompetent),
>>> så the vrrp solution isn't as good as it seems. The easiest solution
>>> is to point the domain to two addresses, one for each pen instance.
>>> Actually, the easiest solution is to install pen on a single server
>>> and forget about it, at least as long as the hardware is reliable.
>>> Ulric
>> You could also use CARP, free and cross platform. Available on
>> OpenBSD, FreeBSD, NetBSD, Linux (
>> Probably will also make it into MacOS X at some point.
>> Cheers,
>> Dom
> Is it pretty much the same as VRRP ? Are there any implementation
> notes/faq/etc online anywhere ? Would it work as the cheapskate example ?

It has some features VRRP lacks, particularly relating to security. In
my experience it works very well at providing fail-over capabilities and
it is pretty easy to use. One thing it does not do well is load
balancing, that is where pen comes in.

Both of these links have practical examples.

As for cheapskate, I don't know what you mean. If anything CARP is
better than VRRP.

> TIA...

Received on Tue Mar 28 2006 - 00:03:38 CEST

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