Re: CARP using Serial to sync

[David Terrell <dbt_(_at_)_develest_(_dot_)_com>]

On Tue, May 11, 2004 at 03:58:33PM -0400, Chuck Yerkes wrote:
> There's an internal 10 pin header that is the second serial port.
> 
> When I did lots and lots of Failover/HA machines we mandated dedicated
> heartbeat interfaces (on separate cards).  This was because the
> Suns COULD get lots and lots of traffic (before network switches
> existed, even) and a heartbeat could get lost.  We dropped SL/IP
> support when Sun's slip stuff proved to be unreliable.
> 
> Veritas can use FC/AL and SCSI for heartbeat.  Since a pair shared
> disk ANYWAY, this makes terrific sense.  And all it needed was the
> "little sister mode" of "hey, you alive?" and response.

This is a really cute idea but even their own techs say "don't use a 
shared disk for heartbeat, nobody does that"

General technique is doing heartbeat across multiple links, preferably
separate cards (not two ports on a quad card), preferably on different
backplanes on bigger iron machines.